HK1061759B - Method and apparatus for time division multiplexed transmission - Google Patents

Description

Method and apparatus for time division multiplexed transmission

Background

I. Field of the invention

The present invention relates to data communication. More particularly, the present invention relates to a novel and improved technique for multiplexing high-speed packet data transmissions with conventional voice/data transmissions in a wireless communication system.

Description of the Prior Art

Modern communication systems are required to support a variety of applications. One such communication system is a Code Division Multiple Access (CDMA) system that supports voice and data communication between users over a terrestrial link. The use of CDMA techniques in multiple access communication systems is disclosed in U.S. patent No. 4,901,307, entitled "spread spectrum multiple access communication system using satellite or terrestrial repeaters", and in U.S. patent No. 5,103,459, entitled "system and method for generating waveforms in a CDMA cellular telephone system". A particular CDMA system (HDR system) is disclosed in U.S. patent application No. 08/963,386 entitled "method and apparatus for high rate packet data transmission" filed on 3/11/1997. These patents are assigned to the assignee of the present invention and are incorporated herein by reference.

Typically, CDMA systems are designed to conform to one or more standards. These standards include "TIA/EIA/IS-95-B Mobile station-base station compatibility Standard for Dual-mode wideband spread-spectrum cellular systems" (IS-95 Standard), "TIA/EIA/IS-98 recommended minimum standards for Dual-mode wideband spread-spectrum cellular Mobile stations" (IS-98 Standard), "third Generation partnership project" (3GPP) provided by International protocols and embodied in a set of documents including document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (W-CDMA Standard), "TR-45.5 physical layer Standard for CDMA2000 spread-spectrum systems" (CDMA2000 Standard), and "TIA/EIA/IS-856 CDMA2000 high-Rate packet data air interface Specification" (HDR Standard). New CDMA standards are continually being proposed and adopted. These CDMA standards are incorporated herein by reference.

Some CDMA systems are capable of supporting multiple types of traffic (e.g., voice, packet data, etc.) on the forward and reverse links. The characteristics of each type of service are generally given by the specific set of requirements, some of which will be described below.

In general, voice services require a fixed and common grade of service (GOS) for all users and a (relatively) strict and fixed delay. For example, a total one-way delay of speech frames of less than 100ms may be specified. These requirements can be met by providing each user with a fixed (and guaranteed) data rate (e.g., by a dedicated channel assigned to the user for the duration of the communication session) and guaranteeing a maximum (tolerable) error rate for the voice frames based on the link resources. To maintain the required error rate at any data rate requires more resources to be allocated to users with degraded links.

In contrast, packet data services can tolerate different grades of service (GOS) for different users and in turn can tolerate varying amounts of delay. Generally, the grade of service (GOS) of a data service is defined as the total delay incurred in error-free data messaging. The transmission delay may be one parameter used to optimize the efficiency of the data communication system.

To support both types of traffic, a CDMA system may be designed and operated at a first allocated transmit power for users requiring a particular grade of service (GOS) and shorter delay. The remaining available transmit power may then be allocated to packet data users that may tolerate longer delays.

In a CDMA system, each transmission source is interference from other transmission sources. Due to the bursty nature of packet data, the transmit power from a transmitting source may fluctuate widely during transmission of a data burst. Fast and wide fluctuations in transmit power can interfere with other transmissions from other sources and degrade the performance of these transmissions.

It can be seen that there is a great need for techniques for efficiently and effectively multiplexing high-speed packet data transmissions with voice and other transmissions.

Summary of The Invention

The present invention provides various techniques for simultaneously supporting voice/data and high-speed packet data services and minimizing the impact of the packet data service on the voice/data service. According to an aspect of the present invention, voice/data and packet data can be multiplexed in one transmission time interval (e.g., one slot), resulting in efficient utilization of available resources. According to another aspect of the present invention, the transmission power from the base station is controlled such that the amount of change in the total transmission power is maintained within a certain range to reduce transmission degradation from this transmission source to other transmission sources (e.g., some base stations).

One particular embodiment of the present invention provides a method for simultaneously transmitting many types of data in a wireless (e.g., CDMA) communication system. According to the method, a first type of data (e.g., voice, overhead, low and medium rate data, delay sensitive data, signaling, etc.) is received and processed according to a first signal processing scheme to produce a first payload. A second type of data (e.g., high speed packet data) is also received and processed according to a second signal processing scheme to generate a second payload. For example, the first signal processing scheme may conform to the W-CDMA or CDMA2000 standards, while the second signal processing scheme may implement, for example, an HDR design.

First and second segments are then defined in the transmission time interval, the first segment being used to transmit the first type of data and the second segment being used to transmit the second type of data. The first and second payloads are then multiplexed into the first and second segments, respectively, and the multiplexed first and second payloads are transmitted. The capacity for the transmission time interval may be selected to be greater than that required for the first payload (e.g., by using a channelization code of shorter length).

The invention further provides other methods, transmitter units (e.g., base stations), receiver units (e.g., remote terminals), and other units that implement various aspects, implementations, and features of the invention, as described in further detail below.

Brief Description of Drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

FIGS. 1A through 1C are diagrams illustrating FDM, TDM, and CDM techniques, respectively, for providing multiple types of traffic to a number of remote terminals in a wireless communication system;

fig. 2A and 2B are graphs of transmit power from a base station in a CDM system for a number of voice/data users and for a number of voice/data and packet data users, respectively;

FIG. 3 is a diagram of a frame format and a slot format of a dedicated physical channel defined for the W-CDMA standard;

FIG. 4 is a simplified block diagram of a communication system in which aspects of the present invention may be implemented;

FIG. 5 is a graph of transmit power for a number of voice/data transmissions and a number of packet data transmissions from a particular base station;

FIGS. 6A and 6B are block diagrams illustrating signal processing at a transmitter for downlink voice/data transmission according to the W-CDMA standard and packet data transmission according to an HDR design; and

fig. 7A and 7B are block diagrams illustrating signal processing at a receiver of downlink voice/data transmission according to the W-CDMA standard and packet data transmission according to the HDR design.

Detailed description of specific embodiments

Fig. 1A through 1C are diagrams illustrating three different techniques for providing multiple types of services to many remote terminals in a wireless communication system. For example, some of these different types of services may include voice, packet data, video, broadcast, messaging, and so on. For example, overhead transmissions typically used for wireless communication systems may include paging, pilot, control channel, and so on. For simplicity, high-speed packet data is referred to herein simply as "packet data," while the remaining types of data (e.g., voice, overhead, some type of medium and low rate data, delay sensitive data, and others) are referred to collectively as "voice/data. Optimization of packet data transmission is an important aspect of efficient spectrum utilization. However, minimizing the impact of packet data transmission in voice/data transmission is also important to maintain the required level of quality of service and reliability.

Fig. 1A illustrates a Frequency Division Multiplexing (FDM) system that supports voice/data and packet data traffic using two frequency bands. As mentioned above, it is generally preferable to separate voice/data and packet data services due to differences in their characteristics and requirements. In an FDM system, a first system (e.g., an IS-95 system) having one carrier signal at a first frequency may support voice/data traffic, while a second system (e.g., an HDR system) having a second carrier signal at a second frequency may support packet data traffic.

Fig. 1B illustrates a Time Division Multiplexing (TDM) system in which transmission occurs over discrete time units, which may be referred to as "slots" in some systems or "frames" in some other systems. For TDM systems, many timeslots are allocated to support voice/data traffic and the remaining timeslots are used to support packet data traffic. In the case of mobile communications (GSM) + General Packet Radio System (GPRS) systems, such TDM systems are global systems. GPRS provides GSM packet data services.

Fig. 1C shows a Code Division Multiplexing (CDM) system. Where voice/data and packet data traffic share the available transmit power. For CDM systems, each voice/data transmission and each packet data transmission is typically channelized by a respective channelization code, so that the transmissions are (ideally) orthogonal to each other. The transmit power of each transmission may be adjusted to maintain the required level of performance. The data load, available transmit power, and other factors govern the number of transmissions that can be simultaneously supported and the data rate of each transmission.

Fig. 2A is a graph of transmit power from a base station in a CDM system, which supports many voice/data users simultaneously. For such CDM systems, the transmit power to each individual user may vary widely due to changes in data rate and path conditions. However, due to statistical averaging, the total aggregate transmit power for all voice/data users typically varies over a small range (percentage wise). Since each voice/data user typically only needs a medium or low data rate, many voice/data users can be supported simultaneously. As the number of voice/data users increases, the statistical averaging improves and the amount of variation in the total aggregate transmit power decreases.

For a wireless communication system, the transmit power from each transmitting source (e.g., each base station) acts as interference to other transmitting sources when they use the same radio resources. For CDM systems, the quality of the signal received by each user is related to the noise and interference experienced by the signal received by the user. Therefore, in order to maintain the required signal quality, it is desirable to have the interference as small and as constant as possible (in general, the system can compensate for gradual changes in interference, but not abrupt changes).

Fig. 2B is a graph of transmit power from a base station in a CDM system, which supports many voice/data and packet data users simultaneously. Due to the bursty nature of packet data traffic, and due to the high peak rates that can be used for packet data transmissions, the total aggregate transmit power for voice/data and packet data users can vary over a greater range in a shorter period of time than if only transmitted to voice/data users. This can be seen by comparing the graph in fig. 2A with the graph in fig. 2B. Larger variations in the total transmit power from a base station may result in greater fluctuations in the signal quality in transmissions from other base stations, which may lead to performance degradation of these transmissions. In addition, large variations in total transmit power may also result in large fluctuations in signal quality in transmissions from this transmitting base station due to multipath and other phenomena.

The disclosed methods and apparatus provide various techniques that may be used to simultaneously support voice/data and packet data services and minimize the impact of the packet data service on the voice/data service. According to one embodiment, voice/data and packet data may be multiplexed in a transmission time interval (e.g., one slot) so as to efficiently utilize available resources. According to another embodiment, the transmit power from a base station is controlled such that the amount of change in the total transmit power remains within a specified range, resulting in reduced degradation of transmissions from this and other base stations.

In many CDM systems, data is transmitted in separate transmission time intervals. In general, the duration of the transmission time interval is defined to provide excellent performance for services supported by the CDM system. For example, for a W-CDMA system, transmission occurs over 10ms radio frames, with each radio frame further divided into 15 slots. Data to be transmitted is segmented, processed and transmitted in defined transmission time intervals.

According to one embodiment, voice/data transmission may be allocated a portion of the transmission time interval (i.e., voice/data segments) while the remaining portion of the transmission time interval (i.e., packet data segments) may be used for high-speed packet data transmission. Voice/data and packet data segments may be defined dynamically based on voice/data load and packet data load and may be implemented through appropriate signaling, as described in further detail below. For example, for various CDM systems, such as W-CDMA systems, CDMA2000 systems, and others, transmission time interval segmentation into voice/data and packet data segments may be achieved. For a better understanding, the segmentation of the transmission time interval of a downlink transmission in a W-CDMA system is now described in particular.

Fig. 3 is a diagram of a frame format and a slot format of a dedicated physical channel defined by the W-CDMA standard. For each type of physical channel, such as downlink dedicated channel (DPCH), Downlink Shared Channel (DSCH), different frame formats are defined by the W-CDMA standard. Data to be transmitted on each physical channel (i.e., traffic data) is segmented into radio frames, each covering a time period of 10ms and including 15 slots, labeled slot 0 through slot 14. Each slot is further divided into one or more fields for carrying a combination of traffic data, overhead data, and pilot data.

As shown in fig. 3, for a dedicated physical channel, the slot 310 includes a first Data (Data1) field 320a, a second Data (Data2) field 320b, a Transmit Power Control (TPC) field 322, a Transport Format Combination Indicator (TFCI) field 324, and a pilot field 326. Data fields 320a and 320b are used to transmit traffic data (e.g., voice, packet data, messages, or other) for a dedicated physical channel. The transmit power control field 322 is used to send power control information to direct the remote terminal to adjust its transmit power on the uplink up or down to achieve a desired level of performance while minimizing interference to other remote terminals. The transport format combination indicator field 324 is used to send information (e.g., bit rate, channelization code, etc.) indicating the format of the dedicated physical channel and the shared physical channel associated with the dedicated physical channel. The pilot field 326 is used to transmit pilot data for the dedicated physical channel.

Table 1 lists some of the slot formats defined by the W-CDMA standard (version V3.1.1) for the dedicated physical channel. The per slot format in table 1 defines the length (in bits) of each field in the slot. As shown in table 1, the bit rate of the dedicated physical channel can be varied over a wide range of values (e.g., from 15Kbps to 1920Kbps), and the number of bits in each time slot varied accordingly. For some slot formats, one or more fields in the slot may be omitted (i.e., length 0).

TABLE 1

According to the W-CDMA standard, many physical channels may be used to transmit data to a particular remote terminal. Each physical channel is channelized with Orthogonal Variable Spreading Factor (OVSF) codes with a specific spreading factor (ranging from 4 to 512 for the downlink). The OVSF code channelizes the physical channel so that transmissions on the physical channel are orthogonal to other transmissions on other physical channels. The OVSF code IS similar to the walsh code used in IS-95 systems to channelize the forward link transmission. The OVSF code for each physical channel is typically determined at the beginning of a communication session and typically does not change during the session.

The spreading factor corresponds to the length of the OVSF code. A smaller spreading factor (e.g., 4) corresponds to a shorter code length and for a higher data rate, while a larger spreading factor (e.g., 512) corresponds to a longer code length and for a lower data rate. As shown in table 1, the total number of bits per slot (and thus the total number of bits available for traffic data) varies over a wide range and is related to the spreading factor used for that slot.

According to one embodiment, the data fields 320a and 320b assigned to the traffic channel in each time slot may be segmented into voice/data segments and packet data segments. Voice/data segmentation may be used for voice/data to be transmitted in a time slot. Packet data may be transmitted using packet data fragments.

For a particular voice/data transmission on a physical channel, the transmitted data bits are segmented and processed as described in more detail below. The voice/data payload of each slot may include any number of data bits (i.e., not necessarily a particular number of bits) according to the W-CDMA standard. Also, the size of the voice/data payload may vary from slot to slot. Depending on the number of bits in the payload, the spreading factor of the OVSF code may be selected accordingly.

As shown in table 1, the spreading factor of OVSF codes ranges from 4 to 512 and is a power of 2. Each spreading factor and slot format is associated with a particular number of data bits that can be transmitted in a slot. The capacity of the time slot can be (roughly) selected using a spreading factor. In general, for a given payload size, the largest possible spreading factor is selected that closely matches the payload.

In the payload of a slot, the number of coded bits may not be equal to the number of data bits available for the selected spreading factor. Thus, the W-CDMA standard defines a rate-matching scheme whereby many coded bits in the payload can be punctured (i.e., erased) or repeated, resulting in rate-matched bits equal to the number of bits available in the slot.

The capacity of the time slot may be defined using the processing mechanism (e.g., spreading) defined by the W-CDMA standard. A portion of the slot capacity may be used for voice/data and the remaining portion may be used for packet data. A "slot segmentation parameter" may be defined and used to identify a particular allocation (e.g., percentage amount) of slots available for packet data and voice/data. The slot segmentation parameter may indicate that the slots are all allocated to voice/data (e.g., slot segmentation parameter 0%), or that the slots are all allocated to packet data (e.g., slot segmentation parameter 100%), or any possible percentage or mixture between these two extremes.

Table 2 lists the slot segments for voice/data and packet data for three different spreading factor groups. For a given voice/data payload, the spreading factor may be selected such that the slot capacity approximately matches the payload. Depending on the particular payload size, different spreading factors may be required, as shown in the second column. If the spreading factor is then reduced to one-half, the slot capacity is approximately doubled, as shown in Table 1. In this case, half of the slot capacity may be allocated to the voice/data payload, while the other half of the slot capacity may be used for packet data, as shown in the third column. Thus, if the spreading factor is reduced by a factor of 2, approximately 50% of the slot capacity may be used for packet data (i.e., the slot segmentation parameter is 50%).

Similarly, if the spreading factor is reduced by a factor of 4, the slot capacity is approximately increased by a factor of 4. One-quarter of the slot capacity may then be allocated to the voice/data payload, while the other three-quarters of the slot capacity may be used for packet data, as shown in the fourth column. Thus, if the spreading factor is reduced to one-fourth, approximately 75% of the slot capacity can be used for packet data (i.e., the slot segmentation parameter is 75%). The spreading factor can be further reduced to further increase the slot capacity and slot segmentation parameters.

TABLE 2

	Spreading factor-voice/data only	Spreading factor-50% capacity for packet data	Spreading factor-75% capacity for packet data
				User 1	16	8	4
User 2	32	16	8
				User 3	64	32	16
User 4	128	64	32

As shown in table 1, the spreading factor has a length that is a power of 2, and the slot capacity is approximately doubled each time the spreading factor is reduced to one-half. A coarse increment in the spreading factor produces a corresponding coarse increment in the slot segmentation parameter (e.g., 0%, 50%, 75%, etc. up to 100%). Fine adjustments of slot segmentation parameters may be obtained by using rate matching mechanisms defined by the W-CDMA system. The slot segmentation parameter may be defined to any particular value (e.g., 20%, 30%, etc.) using rate matching. The voice/data payload may then be matched to the voice/data segment by selecting appropriate rate matching parameters, as described in further detail below. Thus, fine-tuning of the slot segmentation parameters may be performed using rate matching.

Voice/data segmentation may be used for one user and packet data segmentation may be used for the same or different users for each slot of each physical channel. The segments may be mixed and matched between users.

Fig. 3 shows the slot segmentation corresponding to two reduced spreading factors. In slot 330, the spreading factor is reduced to one-half (from S to S/2), and the slot capacity is approximately doubled. Data fields 320a and 320b are segmented into voice/data segments 332 and packet data segments 334. The voice/data segment 332 includes approximately half of the time slots (i.e., the left half in the example shown in fig. 3) and is used for voice/data. Packet data segment 334 includes the remaining half of the time slot and is used for packet data.

Similarly, in slot 340, the spreading factor is reduced to a quarter (from S down to S/4), while the slot capacity is approximately increased by a factor of 4. The data fields 320a and 320b are segmented into a voice/data segment 342 and a packet data segment 344. The voice/data segment 342 includes approximately one-quarter of a time slot and is used for voice/data. Packet data segment 344 includes the remaining three quarters of the time slots and is used for packet data. Other spreading factors may also be used to provide different slot capacities and to provide different percentage allocations between voice/data and packet data (i.e., different slot segmentation parameters).

As shown in table 1, when the spreading factor is reduced by a certain factor (e.g., 2), different slot formats are used. Since the new slot format is typically associated with a different number of extra overhead bits, the payload capacity of the new slot is increased approximately (not very correctly) by a certain factor. The slot segmentation into voice/data segments and packet data segments may be done in various ways.

In a first segmentation embodiment, the slot segmentation parameters are selected based on the voice/data load and the packet data load. For example, if the voice/data load is approximately equal to the packet data load, the spreading factor may be selected to be half the value that has been selected for the voice/data load. Approximately half of the slot capacity is allocated to voice/data and the other half to packet data. Each of the voice/data and packet data may be processed according to the selected slot segmentation parameters, as described in more detail below.

In a second, fragmented embodiment, the voice/data payload is processed first and mapped to the space available in the slot. The packet data may then be multiplexed using any remaining portion of the time slots not used for voice/data. In this embodiment, the slot segmentation parameters are determined after processing the voice/data payload and based on the remaining space available in the slot. To ensure that some space is available for packet data, a smaller spreading factor may be selected.

For a W-CDMA system, a rate matching process may be performed such that a particular number of coded bits of the voice/data payload may be generated to match the number of bit positions available in the voice/data segment. If the payload is larger than the voice/data segment, then many of the coded bits may be punctured (i.e., erased). On the other hand, if the payload is smaller than the voice/data segment, many coded bits may be repeated.

Similar rate matching may also be performed on the packet data to match the payload to the available space in the packet data segment. Alternatively, the packet data payload may be formed to match the packet data segments. Other techniques for mapping packet data payloads to packet data segments are also contemplated and within the scope of the present invention.

In one embodiment, all channels of voice/data may be defined to have the same segment length (not necessarily corresponding to the same payload, as the processing of the channels may be different) for a particular base station. This supports the use of completely different transmission structures (e.g., similar to the structure of an HDR system) in the packet data segment.

The segmentation of the slots and the transmission of both voice/data and packet data in the slots may provide a number of advantages. First, the coupling of voice/data and packet data may be removed. Such decoupling can be achieved, for example, by minimizing the overlap between two segments. The decoupling of voice/data and packet data minimizes the impact of packet data on voice/data and improves the performance of both types of traffic. Second, slot segmentation supports the transmission of both voice/data and packet data on the same carrier. This allows CDM systems to provide users with multiple types of services. Third, the slot segments may support multiple (and independent) channel structures for voice/data and packet data, as described in more detail below. Each channel structure may be specifically designed for the particular type of traffic that the channel is supporting (e.g., different coding and interleaving schemes). Also, some CDM systems, such as W-CDMA systems, may be suitable for slot segmentation in support of the present invention (with possibly minor variations to existing designs).

Fig. 4 is a simplified block diagram of a communication system 400 in which various aspects of the present invention may be implemented. In one particular embodiment, communication system 400 is a (CDMA-based) system that conforms to the W-CDMA standard, the CDMA2000 standard, or some other standard or CDMA design (based). At the transmitter 410 (e.g., base station), voice/data is sent, typically in blocks, from a voice/data source 412a to a Transmit (TX) voice/data processor 414a, which formats, codes, and processes the data to generate coded voice/data. Similarly, packet data is typically sent in blocks from a packet data source 412b to a Transmit (TX) packet data processor 414b, which formats, codes, and processes the data to generate coded packet data.

The encoded voice/data and packet data are then provided to a TDM multiplexer 416, which multiplexes the data into a TDM data stream. The TDM multiplexed data may have the format shown in fig. 3 and is provided to a transmitter (TMTR)418, which filters, (digitally and analog), modulates, (quadrature) amplifies, and upconverts the data to generate a modulated signal. The modulated signal is then transmitted via one or more antennas 420 (only one antenna is shown in fig. 4) to one or more receiver units (e.g., remote terminals).

The processing performed by voice/data processor 414a and packet data processor 414b is dependent on the particular CDMA standard being implemented. Processing for the W-CDMA standard is described further below. Transmit controller 422 may direct the operation of voice/data processor 414a and packet data processor 414b to provide the required output data. The controller 422, in turn, may direct the operation of the TDM multiplexer 416 so as to obtain the desired TDM data stream.

At receiver unit 430, the transmitted signal is received by one or more antennas 432 (again, only one antenna is shown in FIG. 4) and provided to a receiver (RCVR) 434. In receiver 434, the received signal is amplified, filtered, frequency down-converted (quadrature) demodulated, and digitized to produce samples. The samples may be processed, e.g., digitally filtered, scaled, etc., to generate symbols. A TDM Demultiplexer (DEMUX)436 receives and demultiplexes the symbols and provides the voice/data symbols to a Receive (RX) voice/data processor 438a and the packet data symbols to a receive packet data processor 438 b. Each data processor 438 processes the respective received symbol in a manner complementary to the processing and encoding performed at the transmitter 410. The decoded data from the data processors 438a and 438b is then provided to respective data sinks 440a and 440 b.

Receive controller 442 can direct the operation of TDM demultiplexer 436 such that the data symbols are properly demultiplexed and routed to the proper receive data processor. Controller 442 may further direct the operation of the rx data processors 438a and 438b to properly process and decode the data symbols.

The slot segments, slot segment parameters, and signal processing parameters (collectively referred to as processing information) may be signaled by a transmitting source (e.g., a base station) to a receiving device (e.g., a remote terminal) according to various signaling schemes. In one embodiment, the base station may transmit the processing information to the remote terminal on (1) a control channel (e.g., a Common Control Physical Channel (CCPCH) in a W-CDMA system), (2) in its own transmission (e.g., in a control data field in a time slot), or by some other mechanism. In another embodiment, certain processing information may be provided to the remote terminal during the session initialization phase. The remote terminal then stores the information for later use.

The above signal processing supports transmission of various types of services. A two-way communication system supports two-way data transmission. However, for simplicity, the signal processing in the reverse direction is not shown in fig. 4. It should be noted, however, that the reverse link transmission may be common to both types of segmentation, or may be segmented.

Voice/data and packet data may be processed in various ways. In one processing embodiment, voice/data and packet data are processed through two (independent) processing paths that may implement two different processing schemes. Various signal processing schemes may be used such as, for example, CDMA, TDMA, etc. Each processing path may take into account the current slot segmentation parameters and process the voice/data or packet data payload so that it can be mapped to the allocated space in the slot. As shown in fig. 4, two signal processing schemes for voice/data and packet data may be supported by two data processors 414a and 414b at transmitter unit 410 and data processors 438a and 438b at receiver unit 430.

For each processing path, the signal processing scheme for the type of data being transmitted by that path may be specifically selected. For voice/data, signal processing defined by a particular CDMA standard (e.g., the W-CDMA, CDMA2000, or IS-95 standard) or some other CDMA-based design may be used. For packet data, signal processing defined by the same different CDMA standard or some other design (e.g., HDR) may be used. HDR is preferably applied to packet data, providing improved performance over other CDMA signal processing schemes. Thus, voice/data and packet data may be segmented, coded, rate matched, and interleaved according to their respective signal processing schemes.

Although not explicitly shown in fig. 4, the voice/data and packet data may be modulated using the same or two different modulation schemes. For example, modulation schemes that may be used include Phase Shift Keying (PSK), such as quadrature PSK (qpsk) or offset-qpsk (oqpsk), Quadrature Amplitude Modulation (QAM), Orthogonal Frequency Division Multiplexing (OFDM), and others.

In further processing embodiments, voice/data and packet data are processed in accordance with a common signal processing scheme, which may be defined by a particular CDMA standard (e.g., the W-CDMA or CDMA2000 standard) or some other CDMA-based design. However, different sets of parameters may be used for voice/data and packet data. For example, the block length and the interleaving interval of the packet data may be selected to be larger than that of the voice/data. For example, voice/data may be encoded using convolutional coding, while packet data is encoded using Turbo coding. Some newer generation CDMA standards, such as the W-CDMA and CDMA2000 standards, support these different processing schemes. The use of a common signal processing scheme may simplify the design of the transmitter unit and the receiver unit.

In one embodiment, voice/data and packet data are time division multiplexed together into one time slot after signal processing, as shown in fig. 4. At the output of the TDM multiplexer 416, the temporal ordering of the voice/data and packet data approximates the temporal ordering when the data is sent over the air. Multiplexing of TDM voice/data and packet data after signal processing allows decoupling of the two data types, as described in further detail below.

In another embodiment, voice/data and packet data are time division multiplexed together into a time slot prior to signal processing, and then the TDM voice/data and packet data are processed (e.g., according to a general signal processing scheme). Although it is possible to mix voice/data and packet data in this embodiment, various techniques may be used to reduce the impact of packet data on voice/data. For example, for a particular base station, it may be defined that all channels of voice/data have the same segment length. Additional techniques for reducing the impact of packet data on voice/data are described further below.

Improved performance can be obtained if the packet data segments of neighboring base stations (or cells) are approximately aligned in time. By minimizing (to the extent possible) the amount of overlap between voice/data transmissions and packet data transmissions, the amount of interference between the two types of transmissions may be reduced, which may result in improved performance of the two types of transmissions. Alignment of the segments may reduce the burst of packet data transmissions and the impact of high data rates on voice/data transmissions.

Time alignment of packet data segments in neighboring cells can be obtained, for example, by first synchronizing the timing of the cells using timing from Global Positioning System (GPS) satellites. The slot segmentation parameter may be chosen to be the same (e.g., 50%) for a given cluster of cells. The time slots may then be segmented such that the packet data segments of the cells in the cluster overlap as much as possible. Also, the variation in the slot segment parameter may be limited to a specific range. The packet data segments may be aligned using signaling between (neighboring) base stations.

If the packet data load of adjacent cells is different, slot segments may still be defined such that the packet data segments overlap as much as possible. However, for cells with a light packet data load, it may be defined that some slots have no packet data fragmentation (i.e., the slot fragmentation parameter is 0%). If the voice/data and packet data of a particular base station or a group of neighboring base stations overlap, the transmit power of the voice/data segment or the packet data segment, or both, may be adjusted to reduce the impact from the overlap. For example, the transmit power of the voice/data segments may be increased, the transmit power of the packet data segments may be decreased or limited to a particular value (e.g., approximately equal to the value of the voice/data segments in the same time slot, as described below), or a combination thereof.

Also to reduce the amount of overlap between voice/data and packet data, a "guard time" may be provided between the voice/data and packet data. The guard time may be a gap of a particular time duration in which no data of any type is transmitted.

In one embodiment, to support different signal processing schemes and, in turn, to be compatible with other (e.g., older generation) CDMA systems, transmissions on certain (physical) channels may be time division multiplexed to support both voice/data and packet data, and transmissions on certain other channels may be operated to support only voice/data (or possibly only packet data). When the system of the present invention is overlaid with legacy systems, it is generally not possible to align the segments of all downlink channels since some legacy systems do not support segmentation of the channels. In this case, the packet data channel structure may be designed to be consistent with (e.g., orthogonal to) the conventional channel structure in order to minimize interference between channels.

According to another embodiment, to reduce the impact of packet data transmissions on voice/data transmissions, particularly when the two types of transmissions overlap, the transmit power of the packet data transmissions is adjusted to reduce the amount of fluctuation in the total aggregate transmit power from the base station. As shown in fig. 2B, the burstiness and high data rates of packet data transmissions may cause large fluctuations in the total aggregate transmit power from a base station, which may cause large fluctuations in the amount of interference from other transmissions from this and other base stations. The fluctuations in the total aggregate transmit power may be reduced according to various schemes.

Fig. 5 is a graph of transmit power for a number of voice/data transmissions and a number of packet data transmissions from a particular base station. The transmit power for transmitting only all voice/data may be summed for each slot and then the total aggregate voice/data transmit power may be plotted as shown in fig. 5. For mixed voice/data and packet data transmission, the transmit power of all voice/data segments may be summed, and the transmit power of all packet data segments may also be summed. The total aggregate transmit power of the packet data segments can be made approximately equal to the total aggregate transmit power of the voice/data segments as shown in fig. 5.

An "equal" transmit power for voice/data and packet data is available at the "per transmission" level or at the "per base station" level. The transmit power of the packet data segment for each hybrid transmission (e.g., to a particular remote terminal) is maintained approximately equal to the transmit power of the voice/data segment at each transmission level. This ensures that the total aggregate transmit power of the two segments of the many transmissions to the many remote terminals is approximately equal. Implementing equality at each transmitted level is much simpler than implementing equality at each base station level.

At the level of each base station, the transmit power of each packet data segment for the hybrid transmission is allowed to vary relative to the transmit power of the voice/data segment. However, the total aggregate transmit power from the two segments of the base station is kept equal. A controller in the base station allocates the transmit power of each of the hybrid transmitted packet data segments so as to result in an equal total aggregate transmit power.

Fig. 6A and 6B are diagrams of signal processing at transmitter unit 410 for downlink voice/data transmission according to the W-CDMA standard and downlink packet data transmission according to HDR. The downlink refers to transmission from the base station to the remote terminal (or User Equipment (UE), a term used in the W-CDMA standard), and the uplink refers to transmission from the remote terminal to the base station.

The signal processing of voice/data is performed by the voice/data processor 414a shown in fig. 4. The upper signaling layer of the W-CDMA system supports the simultaneous transmission of many transport channels, each capable of carrying voice/data (e.g., voice, video, data, etc.) for a particular communication. Voice/data for each delivery channel is provided in blocks, also referred to as delivery blocks to the corresponding delivery channel processing section 610.

In each transport channel processing section 610, Cyclic Redundancy Check (CRC) bits are calculated using each transport block in block 612. CRC bits are attached to the transport block and used for error detection at the receiver. Then, in block 614, a number of CRC encoded blocks are concatenated together in series. If the total number of bits after concatenation is larger than the maximum size of the coded block, the bits are segmented into a number of (equal size) coded blocks. Each coded block is then coded with a particular coding scheme (e.g., convolutional coding, Turbo coding) or not coded at block 616.

Then, in block 618, rate matching is performed on the coded bits. Rate matching is performed according to the rate matching attribute assigned by the higher signaling layer. According to one embodiment, rate matching is performed in turn in accordance with slot segmentation parameters that define each voice/data segment.

For rate matching on the uplink, some bits are repeated or punctured so that the number of bits transmitted for each voice/data payload matches the number of bits available in the assigned voice/data segment. On the downlink, unused bit positions may be filled with Discontinuous Transmission (DTX) bits in block 620 in accordance with the W-CDMA standard. The DTX bits indicate when transmission should be turned off and not actually transmitted. According to one embodiment, unused bit positions may be advantageously assigned to packet data segments and used for packet data transmission.

The rate matched bits are then interleaved according to a particular interleaving scheme to provide time diversity in block 622. The time interval for performing interleaving may be selected from a set of possible time intervals (e.g., 10ms, 20 ms, 40 ms, or 80 ms) according to the W-CDMA standard. The staggered time interval is also referred to as a Transmission Time Interval (TTI). The TTI is an attribute associated with each transport channel that does not vary for the duration of a communication session according to the W-CDMA standard. As used herein, "traffic" includes some bits in one TTI for a particular transport channel.

When the selected TTI is greater than 10 milliseconds, traffic is segmented and mapped onto successive transport channel radio frames in block 624. Each transfer channel radio frame corresponds to one transmission over a (10 ms) radio frame period. Traffic may be interleaved over 1, 2, 4, or 8 radio frame periods according to the W-CDMA standard.

The radio frames from all active delivery channel processing sections 610 are then serially multiplexed into a coded combined delivery channel (CCTrCH) in block 630. DTX bits are then inserted into the multiplexed radio frame in block 632 such that the number of bits to be transmitted matches the number of bits available on the physical channel for data transmission. Furthermore, according to one embodiment, the position of the DTX bits may advantageously be used for packet data transmission. If more than one physical channel is used, the bits are segmented among the physical channels in block 634. Each physical channel may carry a transport channel with a different TTI. The bits in each radio frame period of each physical channel are then interleaved in block 636 to provide additional time diversity. The interleaved physical channel radio frames are then mapped onto their corresponding physical channels in block 638.

Fig. 6A also shows signal processing at the transmitter unit 410 for downlink packet data transmission according to the HDR design. In block 652, CRC bits are calculated in the data processor 414b using each data packet. CRC bits are appended to the packet and used for error detection at the receiver unit. The CRC bits, data bits, and other control bits (if any) are then formatted in block 654. The formatted packet is then encoded with a particular coding scheme (e.g., convolutional coding, Turbo coding) in block 656. The coded bits are then scrambled with a scrambling sequence assigned to the remote terminal designated to receive the packet data transmission, block 658.

The scrambled bits are then modulated according to a particular modulation scheme in block 660. For example, various modulation schemes (e.g., PSK, QPSK, and QAM) may be used, with the selected scheme being related to the transmit data rate. The modulation symbols are then interleaved at block 662. The symbols may then be punctured or repeated to obtain the desired number of symbols in block 664. The symbols may also be punctured/repeated according to the slot segmentation parameters and the assigned packet data segments. The symbols are then demultiplexed and mapped onto a number of physical channels in block 666.

Fig. 6B is a diagram of signal processing of a physical channel. As shown in fig. 6B, the voice/data for each physical channel is provided to a corresponding physical channel processing section 640 in the data processor 414 a. In each physical channel processing section 640, the data is converted to a complex representation (i.e., in-phase and quadrature components) in block 642, and then the complex data for each physical channel is channelized with a corresponding channelization code (e.g., OVSF code) in block 644 and then spread with a pseudo-noise (PN) spreading code in block 648 to adjust the transmit power for the voice/data transmission.

The processing is performed on the packet data for each physical channel by a corresponding physical channel processing section 670, which typically also performs covering, spreading and scaling. The processed data from all active physical channel processing sections 640 and 670 are then provided to the TDM multiplexer 416. The TDM multiplexer 416 time-division multiplexes the received signal into a certain segment in a time slot. Subsequent signal processing to generate a modulated signal suitable for transmission to a remote terminal is well known in the art and will not be described herein.

Fig. 7A and 7B are diagrams of signal processing at receiver unit 430 for downlink voice/data transmission according to the W-CDMA standard and downlink packet data transmission according to the HDR design. The signal processing shown in fig. 7A and 7B is complementary to the signal processing shown in fig. 6A and 6B. The modulated signal is initially received, conditioned, digitized, and processed to provide symbols to each physical channel for transmission. Each symbol has a particular resolution (e.g., 4 bits) and corresponds to the transmitted bits. The symbols are provided to a TDM multiplexer 436 which provides the voice/data symbols to a data processor 438a and the packet data symbols to a data processor 438 b.

Fig. 7A illustrates signal processing of a physical channel. Voice/data and packet data transmitted on each physical channel can be reproduced by despreading and decovering the received symbols with the determined despreading and decovering codes. As shown in fig. 7A, the voice/data symbols are provided to a number of physical channel processing sections 710. In each physical channel processing part 710, the symbols are despread with the same PN spreading code as used at the transmitter unit in block 712, decovered with the determined channelization code in block 714, and converted to real symbols in block 716. The output of each physical channel processing section 710 comprises the encoded voice/data transmitted on that physical channel. The processing of the packet data may be obtained in a similar manner by the physical channel processing section 750.

Fig. 7B illustrates the processing of voice/data transmissions on physical channels at receiver unit 430 according to the W-CDMA standard. In the data processor 438a, the symbols in each radio frame period for each physical channel are deinterleaved in block 722, and the deinterleaved symbols from all physical channels used for transmission are concatenated in block 724. For downlink transmissions, bits not transmitted (if any) are detected and removed in block 726. The symbols are then demultiplexed into individual transport channels in block 728. The radio frame of each delivery channel is then provided to the corresponding delivery channel processing section 730.

In block 732, transport channel radio frames are concatenated into traffic in each transport channel processing section 730. Each traffic includes one or more transport channel radio frames and corresponds to a particular TTI for transmission. The symbols in each traffic are deinterleaved in block 734 and the non-transmitted symbols (if any) are removed in block 736. Reverse rate matching is then performed to accumulate the repeated symbols and the indicator of the inserted puncture symbol in block 738. Each encoded block in the traffic is then decoded in block 740, and the decoded blocks are concatenated and segmented into their respective transport blocks in block 742. The CRC bits are then used to check each transport block for errors in block 744.

Fig. 7B also shows signal processing at receiver unit 430 for downlink packet data transmission according to the HDR design. At block 760, symbols from a number of physical channels may be multiplexed together in the data processor 438 b. Erasures for punctured bits are then inserted and the repeated symbols are accumulated in block 762. The rate matched symbols are deinterleaved in block 764, demodulated in block 766, descrambled in block 768, and decoded in block 770. The deinterleaving, demodulating, descrambling and decoding are performed complementarily with respect to the processing performed at the transmitter unit. The decoded data is formatted in block 772 and the decoded data packet is checked for errors using CRC bits in block 774.

For a single user, or for two different users, a particular transmitted voice/data segment and packet data segment may be used. To receive two segments in a transmission, the processing portion shown in fig. 7A and 7B may be used. If the remote terminal is only receiving voice/data segments in transmission, only a TDM demultiplexer and voice/data processor are required. Similarly, if the remote terminal is only receiving packet data fragments in transmission, only a TDM demultiplexer and packet data processor are required.

For clarity, various aspects of the present invention have been described for two types of data, i.e., high speed packet data and voice/data. The present invention can be made applicable to more than two types of data. The corresponding segment in the slot supports each type of data.

Also for clarity, various aspects of the invention have been described for a CDMA system that conforms to the W-CDMA standard. The invention may also be adapted to other CDMA-based systems conforming to other CDMA standards, such as the CDMA2000 standard, for example, or to some other CDMA-based design.

The units in transmitter unit 410 and receiver unit 430 may be implemented in various ways. For example, each of the data processors and controllers shown in fig. 4 may be implemented with one or more application specific integrated circuits (ASICs 9), Digital Signal Processors (DSPs), Programmable Logic Devices (PLDs), controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. Also, the ASIC and DSP may be designed to implement multiple ones of the transmitter units (e.g., the combination of data processors 414a and 414b and controller 422) or multiple ones of the receiver units 430 (e.g., the combination of data processors 438a and 438b and controller 442).

The various aspects and embodiments of the invention may be implemented in hardware, software, or a combination thereof. For example, the signal processing described in fig. 6A to 7B may be implemented by software executed on a processor. For a software implementation, the source code may be stored in a memory unit and executed by a processor. The division of the transmission time interval into segments may be implemented by dedicated hardware, software executing on a processor, or a combination thereof.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (25)

1. A method for simultaneously transmitting multiple types of data in a wireless communication system, the method comprising:

receiving and processing the first type of data according to a first signal processing scheme to produce a first payload;

receiving and processing the second type of data according to a second signal processing scheme to produce a second payload;

defining a first segment of a transmission time interval to be used for transmitting a first type of data and defining a second segment of the transmission time interval to be used for transmitting a second type of data;

selecting a particular capacity for transmission time intervals exceeding a first payload requirement based on the length of the channelization codes, wherein the first and second segments are defined based on the selected capacity;

multiplexing the first and second payloads into first and second segments, respectively, during the transmission time interval; and

the multiplexed first and second payloads are transmitted.

2. The method of claim 1, wherein the first type of data comprises voice data and the second type of data comprises high speed packet data.

3. The method of claim 2, wherein the first type of data further comprises delay sensitive data.

4. The method of claim 1, wherein the first and second payloads are time division multiplexed into first and second segments, respectively.

5. The method of claim 1, further comprising:

between the first and second segments in the transmission time interval, a guard time without transmission is provided.

6. The method of claim 1, wherein data is transmitted on a plurality of channels, each channel being defined by a respective set of first and second segments, wherein the first segments of the plurality of channels are aligned.

7. The method of claim 1, wherein the processing of the first type of data comprises:

matching the first payload to a first segment.

8. The method of claim 7, wherein the matching comprises:

puncturing one or more data bits in the first payload if the first payload exceeds the capacity of the first segment, an

Repeating one or more bits in the first payload if the first payload is less than the capacity of the first segment.

9. The method of claim 1, wherein processing each of the first and second classes of data comprises:

the data is covered with channelization codes.

10. The method of claim 9, wherein processing each of the first and second classes of data further comprises:

the data is spread with a spreading sequence.

11. The method of claim 1, wherein each of the first and second signal processing schemes conforms to a particular CDMA standard or CDMA based design.

12. The method of claim 1, wherein the first signal processing scheme conforms to a W-CDMA standard.

13. The method of claim 1, wherein the first signal processing scheme conforms to cdma2000 standards.

14. The method of claim 1, wherein the first and second segments are defined by a segmentation parameter.

15. The method of claim 14, further comprising:

the fragmentation parameter is signaled to a device designated for receiving the multiplexed first or second payload or both.

16. The method of claim 1, wherein the second segments of adjacent transmission sources are defined to be aligned in time.

17. The method of claim 1, wherein a second segment of adjacent transmission sources is defined such that the second segments overlap in a temporal manner.

18. The method of claim 1, wherein a transmit power of the second segment is maintained to be equal to or less than a transmit power of the first segment.

19. A method for receiving Time Division Multiplexed (TDM) transmissions, the method comprising the steps of:

demultiplexing a first payload transmitted in a first segment of a transmission time interval of a TDM transmission, wherein the TDM transmission further includes a second payload transmitted in a second segment of the transmission time interval, the first payload and the second payload being multiplexed within the transmission time interval, wherein a particular capacity is selected for the transmission time interval exceeding a requirement of the first payload according to a length of a channelization code, wherein the first and second segments are defined according to the selected capacity; and

processing the first payload according to a first signal processing scheme.

20. The method of claim 19, further comprising:

demultiplexing the second payload transmitted in a second segment of the transmission time interval; and

the second payload is processed according to a second signal processing scheme.

21. The method of claim 19, further comprising:

signaling representing the first and second segments in the transmission time interval is received.

22. A transmitter unit for transmitting a plurality of types of data in a communication system, the transmitter unit comprising:

a first data processor for receiving and processing data of a first type according to a first signal processing scheme to generate a first payload;

a second data processor for receiving and processing a second type of data according to a second signal processing scheme to produce a second payload;

a multiplexer coupled to the first and second data processors for multiplexing the first and second payloads into first and second segments, respectively, during a transmission time interval, wherein the first segment is defined in the transmission time interval and is for transmitting a first type of data, wherein the second segment is further defined in the transmission time interval and is for transmitting a second type of data, wherein a particular capacity is selected for the transmission time interval exceeding a first payload requirement based on a length of a channelization code, wherein the first and second segments are defined based on the selected capacity; and

a transmitter coupled to the multiplexer to process and transmit the multiplexed first and second payloads.

23. The transmitter unit of claim 22, further comprising:

a controller to define first and second segments in a transmission time interval.

24. The transmitter unit of claim 22, wherein the first type of data comprises voice data and the second type of data comprises high speed packet data.

25. A receiver unit for receiving one or more types of data in a Time Division Multiplexed (TDM) transmission in a communication system, the receiver unit comprising:

a receiver for receiving and processing the TDM transmission to provide a plurality of symbols;

a demultiplexer for receiving and demultiplexing a first payload transmitted in a first segment of a transmission time interval of a TDM transmission, wherein the TDM transmission includes at least one other payload transmitted in at least one other segment of the transmission time interval, the first payload and the at least one other payload being multiplexed within the transmission time interval, wherein a specific capacity is selected for the transmission time interval exceeding a first payload requirement according to a length of a channelization code, wherein the first segment and the at least one other segment are defined according to the selected capacity; and

a first data processor to receive and process the first payload according to a first signal processing scheme to produce first decoded data; and

a second data processor to receive and process the at least one other payload according to a second signal processing scheme to produce second decoded data.