Method and apparatus for efficient use of communication resources in a CDMA communication system

Method and device for effective use of communication resources in code division multi-directional proximity communication system

Scope of invention

The present invention is generally related to the field of communication, and more particularly to communication in a cellular communication system.

Background of the invention

In the code division multi-directional proximity (CDMA) communication system, unnecessary and excessive transmission by users will not only reduce the system capacity, but also cause interference to other users. The communication system can provide communication services, which include wireless transmission of digitized voice, static or dynamic images, text messages and other types of data. The encoder in the transmitter of the communication system receives the data packet for encoding. Each data packet is transmitted in a time frame. After transmitting the data in each frame, the receiving destination will generate a positive or negative approval to decode the data packet. If the data packet is decoded correctly, a positive confirmation will be sent to the transmitter. If the data packet cannot be decoded correctly, a negative acknowledgement will be sent to the transmitter. When receiving a negative approval, the transmitter will retransmit the failed data packet. The retransmission will be performed at a higher power level than the initial transmission. The increased power level relative to the initial transmission can enable the receiving destination to resolve interference and correctly decode the data packet. However, during retransmission, higher power levels will increase interference to other users. Such interference will prevent the decoding of data packets transmitted by other users. As a result, increasing the power level will reduce the throughput and load of the system, resulting in inefficient use of the communication resources.

For this purpose and other purposes, it is necessary to propose a method and device for effective use of communication resources in a communication system.

Description of the invention

The present invention provides a method and device that can effectively use communication resources when a receiving destination cannot decode the data packet in a code division multi-directional proximity communication system. The transmitting terminal is controlled to transmit a data packet through a data frame with a first data transmission rate and a power level. The transmitter is further controlled to retransmit the failed data packet through at least two data frames at the second data transmission rate and the initial transmission power level. A data transmission rate and power level selector selects a second data transmission rate lower than the first data transmission rate. The data transmission rate and power level selector determines the energy of each bit of the data packet based on the ratio of the first and second data transmission rates, and selects the second data transmission rate from the ratio so that each bit It determines that the energy is at the minimum level.

From the detailed description and these drawings presented below, the features, purposes and advantages of the present invention will become more clear. The same reference characters in these drawings are correspondingly regarded as the same throughout the document. And among them: FIG. 1 illustrates a communication system 100 capable of operating according to various embodiments of the present invention; FIG. 2 illustrates a communication system receiver for receiving and decoding received data; FIG. 3 illustrates a communication system transmitter according to various aspects of the present invention , Used to transmit data on the data frame; Figure 4 illustrates the transmission and retransmission of data packets according to various aspects of the present invention; and FIG. 5 illustrates a graph of the energy of each bit relative to the transmission power level according to various aspects of the present invention, and is used to select the data transmission rate of the initial transmission and the subsequent transmission so that the average energy of the bit is at the minimum level.

Detailed description of the preferred embodiment

The various embodiments of the present invention can be implemented in a wireless communication system based on the code division multi-directional proximity (CDMA) technology, which has been disclosed by the Telecommunications Industry Association (TIA) and described in various standards. These standards include the TIA-EIA-95 standard, the TIA/EIA-IS-2000 standard, the IMT-2000 standard and the WCDMA standard, all of which are incorporated herein by reference. A data communication system is also detailed in "TIA/EIA/IS-856 cdma2000 high-speed packetized data air interface specification" and incorporated herein by reference. This system is more particularly capable of implementing the various embodiments of the present invention. A copy of the standard can be obtained by accessing the Internet website http://www.3qpp2.orq, or by writing to the US VA 22201, Arlington, 2500 Wilson Boulevard, TIA, Standards and Technology Department. This standard is generally considered WCDMA, which can be obtained by contacting Valbonne-France, 650 Route des Lucioles-Sophia Antipolis, 3GPP Support Department.

Generally speaking, a novel and improved method and accompanying device provide efficient communication of data rate control information in a CDMA communication system. One or more exemplary embodiments described herein are proposed in the context of a digital wireless data communication system. Although it is advantageous to use within this situation, various embodiments of the present invention can be implemented in various environments or configurations. Generally, the various systems described herein can be implemented using software control processors, integrated circuits, or discrete logic. The data, instructions, commands, information, signals, symbols, and chips referred to in the entire application can be conveniently expressed in terms of voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light domains or light particles, or a combination of the above. In addition, the blocks shown in the various block diagrams may represent hardware or method steps.

FIG. 1 illustrates a general block diagram of a communication system 100 that can operate according to any code division multi-directional proximity (CDMA) communication system standard and implement various embodiments of the present invention. The communication system 100 can be used for voice, data, or both communication. Generally, the communication system 100 includes a base station 101, which provides a number of mobile stations, such as mobile stations 102-104, and communication links between the mobile stations 102-104 and the public exchange telephone and data network 105. Without departing from the main scope and various advantages of the present invention, the mobile station in FIG. 1 can be called a data access terminal, and the base station can be called a data access network. The base station 101 includes some components, such as a base station controller and a base transceiver system. For simplicity, these components are not shown. The base station 101 can also communicate with other base stations, such as the base station 160. A mobile switching center (not shown) can control various operational aspects of the communication system 100 and related to the backhaul line 199 between the network 105 and the base stations 101 and 160.

The base station 101 communicates with each mobile station via a forward link signal in a coverage area. The forward link signals of the target mobile stations 102-104 are summed to form a forward link signal 106, which is then transmitted from the base station 101. Each of the mobile stations 102-104 that have received the forward link signal 106 will decode the forward link signal 106, and retrieve the information targeted to the user. The base station 160 can also communicate with these mobile stations in its coverage area via a forward link signal. The mobile stations 102-104 communicate with the base stations 101 and 160 via corresponding reverse links. Each reverse link is maintained by a reverse link signal, as if corresponding to the reverse link signals 107-109 of the mobile stations 102-104, respectively.

In the soft handover situation, base stations 101 and 160 can communicate with a common mobile station. For example, the mobile station 102 is located quite close to the base stations 101 and 160, which can maintain communication with the two base stations 101 and 160. On the forward link, the base station 101 transmits on the forward link signal 106, and the base station 160 transmits on the forward link signal 161. On the reverse link, the mobile station 102 transmits the reverse link signal 107 so that both base stations 101 and 160 can receive it. For transmitting a data unit to the mobile station 102 in the soft handover, the base stations 101 and 160 will synchronously transmit the same information to the mobile station 102. On the reverse link, the two base stations 101 and 160 will try to decode the traffic data transmission from the mobile station 102. The base stations 101 and 160 also transmit a pilot channel on the forward link to assist the mobile stations in decoding each channel on the forward link.

Figure 2 illustrates a block diagram of a receiver 400 for processing and demodulating received CDMA signals. The receiver 400 is used to decode the information on the reverse and forward link signals. The received (Rx) samples are stored in RAM 404. The received samples are generated by a radio frequency/intermediate frequency (RF/IF) system 490 and an antenna system 492. The antenna system 492 receives an RF signal, and then sends the RF signal to the RF/IF system 490. The RF/IF system 490 can be any common RF/IF receiver. The received RF signal is filtered, down-converted and digitized to form the Rx sample at the baseband frequency. These samples are provided to a demultiplexer (demux) 402. The output of the demultiplexer 402 is provided to a searcher unit 406 and a finger component 408. A control unit 410 is connected with those (thereto). A combiner 412 connects a decoder 414 to the instruction service element 408. The control unit 410 can be a microprocessor controlled by software, and can be on the same or independent integrated circuit. The decoding function of the decoder 414 is a sequential decoder or a turbo decoder according to the soft output Viterbi law.

During operation, the received samples are provided to the demultiplexer 402. The demultiplexer 402 provides these samples to the searcher unit 406 and the instruction service element 408. The control unit 410 is equipped with an instruction service component 408 to perform demodulation of the received signal under different time offsets according to the search result of the searcher unit 406. The result of the demodulation will be transmitted to the decoder 414 after being combined. The decoder 414 decodes the received data symbol, and then outputs the decoded data symbol. The de-stretching of these channels is performed by multiplying the received sample by the complex conjugate of the virtual noise (PN) sequence, and assigning the Walsh function under a single timing assumption, usually by an integral and dumping (dump) The accumulator circuit (no display) digitally filters the result sampling. These techniques are generally known in the art.

Figure 3 illustrates a block diagram of a transmitter 300 for implementing various aspects of the present invention. A traffic channel data for transmission is input to a modulator 301 for modulation. The modulation is based on any generally known modulation technique, such as Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK) or Binary Phase Shift Keying (BPSK). The data is encoded in the modulator 301 at a data transmission rate. The data transmission rate is selected by a data transmission rate and power level selector 303. The selection of the data transfer rate is based on the feedback information from the receiving destination. The information includes the data transfer rate request of the receiver and the report of the channel status. The data transmission rate and power level selector 303 selects the data transmission rate in the modulator 301 according to these. The output of the modulator 301 is transmitted through a signal expansion operation, and then amplified in block 302 for transmission from the antenna 304. A pilot signal is also generated in block 307. The pilot signal is amplified to an appropriate level in block 307. The pilot signal power level is based on the channel conditions at the receiving end. The combined signal will be amplified in the amplifier 309 and then transmitted from the antenna 304. The data transmission rate and power level selector 303 also selects a power level for the amplification level of the transmitted signal according to the feedback information. The combination of the selected data transmission rate and the power level enables the data transmitted at the receiving destination to be properly decoded. After each transmission of a data frame, the receiving destination sends a confirmation to the transmission source. If the data frame is decoded correctly, the confirmation is positive. If the data frame is not decoded correctly, a negative approval will be sent.

According to various aspects of the present invention, in the communication system 100, a data packet is transmitted through a data frame at a first data transmission rate and a power level from a transmitter 300 of a transmission source such as the mobile station 102. A receiving destination such as base station 101 or 106 receives the data packet. When the receiving destination cannot decode the received data packet, the receiving destination will send a negative approval to the transmitting source. The transmitting source will retransmit the data packet at a second data transmission rate and at the original power level by at least two data frames. According to an embodiment, the second data transmission rate is lower than the first data transmission rate. In this way, the communication resources will be effectively used because the retransmission is performed at the power level of the initial transmission. Used in the retransmission, the number of frames used to transmit the data frame depends on the ratio of the first and second data transmission rates. When the second data transmission rate is half of the first data transmission rate, the retransmission will retransmit each data bit of the frame 450 and 451 of the data packet through two data frames. When the second data is 1/3 of the first data transmission rate, the retransmission will retransmit each data bit of the data packet through a three-data frame.

Referring to FIG. 4, two examples of frames 450 and 451 for transmitting a data packet according to various embodiments of the present invention are illustrated. In the first example 450, the first transmission of these frames 1-6 and the retransmission of frame 2 are explained. The retransmission of the frame 2 occurs, for example, due to receiving a negative approval from the receiving destination. As shown in the figure, the retransmission of frame 2 occurs on two frames. During the transmission, the data transmission rate of the data packet is half of the data transmission rate used in the initial transmission of the data frame 2. Therefore, the retransmission of the data frame 2 uses at least two data frames. Although the power level of each frame remains unchanged, according to one aspect of the present invention, the average energy per information bit becomes nearly twice. The receiving destination, as a result, since the average energy of each bit in the data packet is increased, the data packet can be more successfully decoded. In the second example 451, the retransmission is by three data frames. The data transfer rate during the retransmission period is 1/3 of the data transfer rate used during the initial transmission period. The power level during retransmission is almost the same as the power level used in the initial transmission. In this example, the average energy per bit in the data packet is 3 times the average energy per bit in the data packet used during the initial transmission. In this way, the receiving destination can more successfully decode the data. Because the power level remains unchanged according to various aspects of the present invention, no additional interference is generated. Therefore, the communication resource is used more efficiently.

According to other embodiments, the second data transmission rate is selected from a set of predetermined data transmission rates for transmission. Depending on the power level of the initial transmission, the data transmission rate for the set of transmissions has at least one data transmission rate for the transmission to effectively use the communication resource. In order to determine the data transmission rate for retransmission, it is necessary to determine the bit energy of the data packet in the case of a first data transmission rate and a possible second data transmission rate. The second data transmission rate is selected so that in the case of the power level of the first transmission, the energy determined per bit is at the minimum level.

Referring to FIG. 5, a graph 500 illustrates the selection of the second data transmission rate according to the transmission power level. The horizontal axis "P" 501 indicates the range of the power level, which is used for the initial transmission. The vertical axis Eb 502 indicates that the energy per bit of the data packet is successfully transmitted, and the final frame error rate is reached after the retransmission is completed. These curve traces 503-505 illustrate the power level and the energy per bit under different ratios of the first and second data transmission rates. These curved trajectories 503-505 are exemplary trajectories and are used for illustration. The curved traces 503-505 drawn for a system and a channel status are substantially different from the displayed traces. The relative positions of these trajectories on the graph are also different, which essentially depends on several factors including channel conditions, modulation architecture and coding architecture used in the system. In either case, these curved tracks 503-505 have at least the minimum energy per bit level. For example, for the curve trace 503 corresponding to half of the data transmission rate, the minimum energy per bit level corresponds to a power level 506. Similarly, for the curved track 504 corresponding to 1/3 of the data transmission rate, the minimum energy per bit level corresponds to a power level 507. For the curve trace 505 corresponding to 1/4 of the data transmission rate, the minimum energy per bit level corresponds to a power level 508.

The power level of the initial transmission and subsequent retransmissions are maintained at nearly the same level according to aspects of the present invention. If the power level of the initial transmission is closer to, for example, the power level 506, the second data transmission rate on the retransmission will be selected as half of the data transmission rate of the initial transmission. The power levels of the retransmission and the initial transmission also have the same power level. Therefore, for the completed transmission, the combined energy per bit is at the minimum level. In this way, the communication resource will be used more efficiently. If the power level of the transmission is closer to, for example, the power level 507, the second data transmission rate on the retransmission will be selected as 1/3 of the data transmission rate of the initial transmission. Therefore, for the completed transmission, the combined energy per bit is at the minimum level. In this way, the communication resource will be used more efficiently. If the power level of the transmission is closer to, for example, the power level 508, the second data transmission rate on the retransmission will be selected as 1/4 of the data transmission rate of the initial transmission. Therefore, for the completed transmission, the combined energy per bit is at the minimum level. In this way, the communication resource will be used more efficiently. The data transmission rate and power selector 303 selects the retransmission data transmission rate according to the transmission power level corresponding to the minimum energy per bit as represented by the curved traces 503-505. In this way, for the case of successfully transmitting a data packet, the total energy per bit is minimized.

In order to determine these curve trajectories 503-505, the target frame error rate (FER) of the completed transmission must be known. The target FER after retransmission is equal to the initial transmission FER (FER1) multiplied by the second transmission FER (FER2) (ie FER=FER1*FER2). If the retransmission is delayed for a relatively long time, the initial and subsequent retransmissions will be regarded as mutually unrelated transmissions. The communication system 100 can also transmit a pilot channel according to the standards incorporated herein by reference. Therefore, the FER of a transmission depends on the ratio of the power level of the traffic channel to the pilot channel. Once the target FER, the transmission power level, the pilot channel power, and the possible ratio of the initial transmission to the retransmission data transmission rate are known, the FER2 can be determined. Using FER2, the total energy per bit combined with the initial and retransmission of the data packet can be determined. The curve traces shown in the graph 500 can be displayed in more detail by adjusting the power level when the data transfer rate and target FER remain unchanged. This procedure will be repeated with different data transfer rate ratios. For different data transfer rate ratios, in the case of a target FER, the minimum energy of each bit position on the curve track can be confirmed. If different target FERs are required, the procedure will be repeated for different values of FER targets. The possible curve trajectory of a channel condition can be determined by the data transmission rate and power level selector 303, which enables the data transmission rate of the retransmission to be determined in time and allows the retransmission to occur without delay or considerable delay . In one embodiment, it is appropriate to use a processor.

Those who are familiar with the art should have a good understanding of the various graphical logic blocks, modules, circuits, and rules related to the embodiments disclosed here. These can be made using electronic hardware, computer software, or a combination of the two. to realise. In order to clearly illustrate the interchangeability of hardware and software, various icon components, blocks, modules, circuits, and steps have generally been described above in terms of their functions. Whether these functions are implemented by hardware or software, it depends on the special application and design constraints imposed on the entire system.

a. The various iconic logic blocks, modules, and circuits of the embodiments disclosed herein can use general-purpose processors, digital signal processors (DSP), special application integrated circuits (ASICs), and field programming gate arrays ( FPGA) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, or any combination thereof are designed and implemented or executed to perform the functions described herein. The general-purpose processor may be a microprocessor, but on the other hand, the processor may also be any common processor, controller, microcontroller, or state machine. The microprocessor can also be implemented as a combination of arithmetic devices, such as a combination of a digital signal processor (DSP) and a microprocessor, multiple microprocessors, and one or more microprocessors in combination with a digital signal processor core. , Or any other such configuration.

b. The steps related to the methods and rules described in the embodiments disclosed herein can be directly implemented by hardware, or implemented by a software module executed by a processor, or a combination of the two. The software module can reside in dynamic access memory (RAM), flash memory, read-only memory (ROM), erasable programmable read-only memory (EPROM), and electronically clear programmable read-only memory (EEPROM), registrar, hard disk, removable hard disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is connected to the processor so that the processor can read and write data to the storage medium. On the other hand, the storage medium can be integrated into the processor. The processor and storage medium can reside in an application-specific integrated circuit (ASIC). Special application integrated circuits can be resident in the user terminal. On the other hand, the processor and the storage medium can reside in the user terminal as discrete components.

The preferred embodiments described above are provided for anyone who is familiar with the art to make or use the present invention. Various modifications to these embodiments are quite easy for those skilled in the art, and the basic principles defined here can be applied to other embodiments as long as they do not violate the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments disclosed herein, but can be based on the maximum scope consistent with the principles and novel features disclosed herein.