Method of communication between devices operating within a wireless communication system

A subscriber station (SS) utilizes uplink resources that have been assigned to it for communicating with an infrastructure station to exchange data with a neighboring SS while maintaining its link to the infrastructure station. This is accomplished by the SS receiving an uplink allocation from the infrastructure station, transmitting a subscriber-to-infrastructure station header and trailer to the infrastructure station using the modulation and coding scheme (MCS) assigned by the infrastructure station and also transmitting a subscriber-to-subscriber (S2S) message payload, optionally using a second MCS level appropriate for the link between itself and the receiving SS. The subscriber to infrastructure station message is composed so that it occupies the first m codewords and contains a header that describes the length of the subscriber to infrastructure station message. The subscriber to infrastructure station message, then, is followed by the S2S message, composed to occupy the remaining symbols of the allocation.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communication systems and more particularly to a method of communication between devices operating within a wireless communication system.

BACKGROUND

Many wireless communication systems today are composed of a number of fixed base stations (BS) which are distributed geographically over a network coverage area and are communicatively coupled together either via wired links or wireless links. Wireless communication devices (also referred to as “subscriber stations (SSs)”, mobile devices, and the like) within coverage of a base station can communicate via the base station with other subscriber stations within coverage of the base station.

Time Division Duplexing (TDD) refers to a transmission scheme that allows an asymmetric flow for uplink and downlink transmission which is more suited to data transmission. In a Time Division Duplex system, a common carrier is shared between the uplink and downlink, the resource being switched in time. Users are allocated one or more timeslots for uplink and downlink transmission.

Examples of TDD scheduled mobile radio systems include communication systems operating using Time Division Code Division Multiple Access (TD-CDMA) air interface, Time Division Synchronous Code Division Multiple Access (TD-SCDMA), Digital Enhanced Cordless Telecommunications (DECT), Institute of Electrical and Electronics Engineers (IEEE) 802.16 Worldwide Interoperability for Microwave Access (WiMAX), and Long Term Evolution (LTE).

For example, Institute of Electrical and Electronics Engineers (IEEE) 802.16 is a point-to-multipoint (PMP) system with one hop links between a base station (BS) and a subscriber station (SS). Any of the IEEE standards or specifications referred to herein may be obtained at http://standards.ieee.org/getieee802/index.html or by contacting the IEEE at IEEE, 445 Hoes Lane, PO Box 1331, Piscataway, N.J. 08855-1331, USA. The Institute of Electrical and Electronics Engineers (IEEE) 802.16 Working Group on Broadband Wireless Access Standards is a unit of the IEEE 802 LAN/MAN Standards Committee that aims to prepare formal specifications to support the development and deployment of broadband Wireless Metropolitan Area Networks.

LTE (Long Term Evolution) refers to a new air interface that is being developed by 3GPP in its Release 8 Specification set. Any of the 3GPP standards or specifications referred to herein may be obtained at http://www.3gpp.org/specifications.

LTE will provide users with an experience similar to that of fixed line broadband both in terms of bandwidth and latency, meaning applications that can be delivered today on fixed line will soon be available over the air and fully mobility with LTE.

Time Division Duplexing (TDD) systems such as IEEE 802.16 and similar mobile/base style systems, such as LTE, provide no method of transmitting data directly between subscriber stations (SS). Instead, all data transferred from one SS to another must be sent through the base station (BS). A more efficient method of transferring data is to send it directly from one SS to another. However, as the standards do not currently support this functionality, a method of providing the functionality without modifying the standards is desired.

Accordingly, there is a need for a method and apparatus for enhanced subscriber-to-subscriber communication within a wireless communication system.

DETAILED DESCRIPTION

A method is provided herein whereby a subscriber station (SS) may use uplink resources that have been assigned to it for communicating with an infrastructure station such as a base station (BS) or a relay station (RS) to exchange data with a neighboring SS while maintaining its link to the infrastructure station. It does this by receiving an uplink allocation, for example, from a base station, transmitting a subscriber-to-infrastructure station header and trailer to the infrastructure station using the modulation and coding scheme (MCS) assigned by the infrastructure station and also transmitting a subscriber-to-subscriber (S2S) message payload, optionally using a second MCS level appropriate for the link between itself and the receiving SS. The subscriber station to infrastructure station message is composed so that it occupies the first m codewords and contains a header that describes the length of the subscriber station to infrastructure station message. The subscriber station to infrastructure station message, then, is followed by the S2S message, composed to occupy the remaining symbols of the allocation. This second part is hidden behind the portion that the infrastructure station will attempt to process, so the infrastructure station is effectively unaware of its contents. The CRC or similar error detection mechanism is calculated based on how data transmitted at a first MCS would be interpreted by a station receiving that data and expecting a second MCS. This approach does not require any changes to infrastructure station equipment and can be implemented completely in subscriber devices. This approach allows a single transmission to be received and meaningfully interpreted by multiple stations. It allows existing systems to be retrofitted with direct link capabilities without requiring an upgrade to the existing infrastructure.

FIG. 1illustrates a wireless communication network for use in the implementation of at least some embodiments.FIG. 1illustrates a particular non-limiting example of one network configuration, specifically an IEEE 802.16 network100. As illustrated, the network100includes at least one base station105for communication with a plurality of subscriber stations110-n(also known as mobile stations). It will be appreciated that although only one base station is illustrated inFIG. 1for simplicity purposes, any number of base stations can be included within the network100. The network100further includes a plurality of relays115-n(also known as relay stations or repeaters). The relays115-nare deployed in the areas with poor coverage and relay transmissions so that subscriber stations110-nin a cell boundary can connect using high data rate links. In some cases relays115-nmay also serve subscriber stations110-nthat are out of the coverage range of the base station105. In some networks, the relays115-nare simpler versions of the base station105, in that they do not manage connections, but only assist in relaying data. Alternatively, the relays115-ncan be at least as complex as the base station105. Further, all or some of the relay stations115can be deployed in a multi-hop pattern. In other words, some relays such as115-6communicate with the base station105via other relays such as115-5. Further, these relays can be within each other's coverage. RS5115-5is considered to be an ascendant station (i.e., a station through which RS6115-6communicates with the BS) for RS6115-6and RS6115-6is considered to be a descendant station for RS5115-5.

FIG. 2illustrates an infrastructure station such as a base station105or a relay station115ofFIG. 1in accordance with at least some embodiments. As illustrated, the infrastructure station comprises a plurality of ports200-n, a controller205, and a memory210.

Each port200-nprovides an endpoint or “channel” for network communications by the infrastructure station. Each port200-nmay be designated for use as, for example, an IEEE 802.16 port or a backhaul port. For example, the infrastructure station can communicate with one or more other base stations and/or relay stations and/or one or more subscriber stations within an 802.16 network using an IEEE 802.16 port. An IEEE 802.16 port, for example, can be used to transmit and receive both data and management information.

A backhaul port similarly can provide an endpoint or channel for backhaul communications by the infrastructure station. For example, the infrastructure station can communicate with one or more other infrastructure stations using the backhaul, which can be wired or wireless, via the backhaul port.

Each of the ports200-nare coupled to the controller205for operation of the infrastructure station. Each of the ports employs conventional demodulation and modulation techniques for receiving and transmitting communication signals respectively, such as packetized signals, to and from the infrastructure station under the control of the controller205. The packetized data signals can include, for example, voice, data or multimedia information, and packetized control signals, including node update information.

The controller205includes a scheduler230for the management of both uplink and downlink communication with the various subscriber stations (SS)110-nand relay stations (RS)115-nassociated with the infrastructure station. It will be appreciated by those of ordinary skill in the art that the scheduler230can be hard coded or programmed into the infrastructure station during manufacturing, can be programmed over-the-air upon customer subscription, or can be a downloadable application. It will be appreciated that other programming methods can be utilized for programming the scheduler230into the infrastructure station. It will be further appreciated by one of ordinary skill in the art that the scheduler230can be hardware circuitry within the infrastructure station. In accordance with the present invention, the scheduler230can be contained within the controller205as illustrated, or alternatively can be an individual block operatively coupled to the controller205(not shown).

To perform the necessary functions of the infrastructure station, the controller205is coupled to the memory210, which preferably includes a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and flash memory.

It will be appreciated by those of ordinary skill in the art that the memory210can be integrated within the infrastructure station, or alternatively, can be at least partially contained within an external memory such as a memory storage device. The memory storage device, for example, can be a subscriber identification module (SIM) card.

FIG. 3is an electronic block diagram of a subscriber station110in accordance with at least some embodiments. The terminology “subscriber station” and “mobile station” are used interchangeably herein to refer to subscribers who may be fixed, nomadic or mobile. As illustrated, the subscriber station110includes an antenna300, a transceiver (or modem)305, a processor310, and a memory315.

The antenna300intercepts transmitted signals from one or more base stations105, one or more relay stations115, and/or one or more subscriber stations110within the network100and transmits signals to the one or more base stations105, one or more relay stations115, and/or one or more subscriber stations110within the network100. The antenna300is coupled to the transceiver305, which employs conventional demodulation techniques for receiving and transmitting communication signals, such as packetized signals, to and from the subscriber station110under the control of the processor310. The packetized data signals can include, for example, voice, data or multimedia information, and packetized control signals, including node update information. When the transceiver405receives a command from the processor310, the transceiver305sends a signal via the antenna300to one or more devices within the network100. For example, the subscriber station110can communicate with one or more base stations and/or one or more relay stations and/or one or more subscriber stations within an 802.16 network by the antenna300and the transceiver305using IEEE 802.16, for example, to transmit and receive both data and management information.

In an alternative embodiment (not shown), the subscriber station110includes a receive antenna and a receiver for receiving signals from the network100and a transmit antenna and a transmitter for transmitting signals to the network100. It will be appreciated by one of ordinary skill in the art that other similar electronic block diagrams of the same or alternate type can be utilized for the subscriber station110.

Coupled to the transceiver305, is the processor310utilizing conventional signal-processing techniques for processing received messages. It will be appreciated by one of ordinary skill in the art that additional processors can be utilized as required to handle the processing requirements of the processor310.

To perform the necessary functions of the subscriber station110, the processor310is coupled to the memory315, which preferably includes a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and flash memory. It will be appreciated by those of ordinary skill in the art that the memory315can be integrated within the subscriber station110, or alternatively, can be at least partially contained within an external memory such as a memory storage device. The memory storage device, for example, can be a subscriber identification module (SIM) card.

In most (time division duplex) TDD scheduled mobile radio systems, such as LTE and 802.16, subscriber stations (SS) request uplink resources from an infrastructure station such as a relay station (RS) or a base station (BS). The infrastructure station allocates uplink resources and assigns a Modulation and Coding Scheme (MCS) to those resources. Subscriber stations may use the assigned resources only for transmitting data directly to the infrastructure station.

It will be appreciated by those skilled in the art that although the remaining embodiments are described in terms of a transmitting subscriber station communicatively coupled to a base station and another subscriber station coupled to the same base station, alternative embodiments of implementation within the scope of the invention include, and are not limited to a subscriber station and a relay station, and also the two subscriber stations can be connected to the same or different base stations or the same or different relay stations or any combination, thereof.

FIG. 4illustrates one embodiment of a transmission structure in which the resources are used to transmit data directly to a neighboring SS by encoding a portion of the transmission at the MCS instructed and expected by a BS and optionally a second portion of the data at a second MCS receivable by a neighboring SS. This can be done even in the case where the base station is not expecting a subscriber to subscriber exchange. By carefully structuring the transmission, the portion of the data intended for the neighboring SS will be located such that the BS is not aware that the subscriber to subscriber data is being transmitted.

As illustrated inFIG. 4, codewords [1, m]400are transmitted at the subscriber station to base station MCS and codewords [m+1, n]405are transmitted at the subscriber station to subscriber MCS. Codewords [1, m]400include a Media Access Control (MAC) header (SBHb)420, uplink (UL) data (ULb)425, a cyclic redundancy check (CRC) (SBTb)430, a subscriber to subscriber header (SSHb)435, and a portion (SSSB-Hb)440of an embedded subscriber to subscriber packet payload. Codewords [m+1, n]405include a second portion (SSSS—b)445of the embedded subscriber to subscriber packet payload.

The subscriber station to base station payload (SBb)410includes the Media Access Control (MAC) header (SBHb)420, the uplink (UL) data (ULb)425, and the cyclic redundancy check (CRC) (SBTb)430. The subscriber station to subscriber station payload (SSb)415includes the subscriber to subscriber header (SSHb)435and both the portion (SSSB-Hb)440and the second portion (SSSS—b)445of the embedded subscriber to subscriber packet payload.

FIG. 5illustrates an alternative embodiment of a transmission structure in which the resources are used to transmit data directly to a neighboring SS. In this embodiment, the subscriber to subscriber portion of the transmission begins in the first codeword after the subscriber station to base station portion of the transmission (i.e. codeword m+1). Whatever parts of the first m codewords that are not filled by uplink data messages are filled with pad bits.

As illustrated inFIG. 5, codewords [1, m]500are transmitted at the subscriber station to base station MCS and codewords [m+1, n]505are transmitted at the subscriber station to subscriber MCS. Codewords [1, m]500include a Media Access Control (MAC) header (SBHb)520, uplink (UL) data (ULb)525, a subscriber to subscriber header (SSHb)530, a cyclic redundancy check (CRC) (SBTb)535, and a pad540. Codewords [m+1, n]505include the embedded subscriber to subscriber packet payload545.

The subscriber station to base station payload (SBb)510includes the Media Access Control (MAC) header (SBHb)535, the uplink (UL) data (ULb)525, the subscriber to subscriber header (SSHb)530, and the cyclic redundancy check (CRC) (SBTb)535. The subscriber station to subscriber station payload (SSb)515includes just the embedded subscriber to subscriber packet payload545.

Although it will be appreciated that either embodiment can be implemented, subsequent discussions hereinafter will revolve around the method described previously and illustrated inFIG. 1.

An SS wishing to transmit data directly to another SS using resources allocated for an SS-to-BS (S2B) link encodes and modulates the first m codewords of its transmission using an MCS (SBMCS) dictated by the BS (seeFIG. 4). The SBMCSis composed of a rate (SBrate) and modulation (SBmod). The first m codewords are comprised of at least any messages expected by the BS including optional uplink data messages. Some of the first m codewords may optionally contain a header instructing the receiving SS how to decode the transmission in order to recover the S2S payload portion. The mthcodeword may also include a portion of the S2S payload as necessary to fill the codeword.

The remaining portion of the transmission, the portion beginning after the mthand up to and including the nthcodeword, are encoded and modulated either at the MCS (SBMCS) dictated by the BS, or optionally at an MCS (SSMCS) achievable between the pair of SSs and ideally optimized for the number of symbols available in this region. The coding rate and modulation chosen for this link are labeled SSrateand SSmod. The S2S data transmitted at the SSMCSis comprised of any payload portion of the transmitted message that was not contained in any of the first m codewords.

In order to prevent the BS from attempting to process the transmitted data that exists after the S2B message, the transmitting SS composes the size, length or similar field of the S2B header to indicate that the S2B data is the extent of the message. For example, if the total of all the uplink data messages were 100 bytes followed by 1500 bytes of S2S data, then the length field of the S2B header should be set equal to 100 bytes assuming that the header describes the total transmission length. This should prevent the BS from attempting to process anything beyond the first 100 bytes of the transmission.

The transmitting subscriber station also composes error detection or correction mechanisms, such as a cyclic redundancy check (CRC), checksum, parity bit array, etc, accordingly. That is, the mechanism only covers the S2B portion of the transmitted message (i.e. the first SBHb+ULbbits) and should not cover the S2S portion, though a second error detection or correction mechanism may be included to cover that part.

The parameters required to receive the S2S portion of the transmission could be known by the receiving SS a priori, calculated from the known transmission parameters or included in the transmission. If the receive parameters are not known a priori and cannot be calculated, then they must be communicated to the receiving SS in some way. One way to do this is to place a header containing receive parameters somewhere in the first m codewords, which are sent using the SBMCS. The receiving SS would demodulate and decode codewords at the SBMCSuntil the header is found, at which point the station would learn the location of the S2S payload transmitted using the SSMCS. The S2S header could be placed after all of the S2B data, as shown inFIG. 4, or could be placed inside of the uplink data, as shown inFIG. 5. The receiving SS could learn the SBMCSby receiving broadcast resource assignments, such as the 802.16 UL-MAP. Alternately, the S2S header could be included at a fixed rate and placed at a known symbol offset into the allocation. In either case, the S2S header could be used to transport fields such as the SSMCSused, the number of SSMCSsymbols, the number of S2S payload bits, etc. There are likely other methods, such as using predefined fixed S2S parameters, to achieve a similar effect.

The embedded S2S payload is encoded at the SSMCS. The BS will demodulate and decode the entire received transmission using SBMCS. Provided there are favorable channel conditions, the first m codewords, which contains the MAC header, any uplink traffic, and potentially an S2S header and a portion of the S2S payload, will be demodulated and decoded without error by the BS. Because the length, size or similar field of the transmitted MAC header describes the message as being contained only within the first m codewords, the BS ignores all data that occurs after the indicated number of bytes. As a result, the error detection or correction mechanism should operate without fault even though an incorrect MCS was used to decode the transmission of codewords [m+1, n]

FIG. 6illustrates an operation600of a transmitting subscriber station when composing its transmission to a BS and a neighboring SS in accordance with some embodiments.FIG. 7illustrates the operation ofFIG. 6in terms of the various components of the data transmission700in accordance with some embodiments.

The operation600, as illustrated, begins with Step605in which the transmitting SS determines the length of the header (705), uplink messages (710), subscriber-to-subscriber (S2S) payload (715) and trailer (It will be appreciated by those of ordinary skill in the art that the trailer is the CRC for the first m codewords). The calculations of transmit durations in symbols and bits will be discussed hereinafter with regards to Tables 1 through 3.

Next, in Step610, the transmitting subscriber station composes the S2S message to be transmitted such that it occupies SSbbits including all embedded headers, where SSbrepresents the number of unused bits from the first m codewords and the number of unused bits from the last n−m+1 codewords. The S2S payload is segmented or aggregated as necessary and pad bits are added as needed.

Next, in Step615, the transmitting subscriber station encodes (encoder732) the header (705), uplink data messages (710), S2S header (712) and first SSSB—Hbbits (718) of the S2S payload using the SBMCS.

Next, in Step620, the transmitting subscriber station encodes (encoder725) SSSS—bS2S payload bits (720) in the range (SSSB—Hb, SSb) at the SSrategenerating codewords [m+1, n].

Next, in Step625, the transmitting subscriber station modulates (modulator735) codewords [1, m] (the subscriber-to-base header (705), uplink messages (710), S2S header (712) and first bits of the S2S payload (718)) (head bits730) using SBmodgenerating pad symbols as necessary and stores all produced symbols (symbols740).

Next, in Step630, the transmitting subscriber station modulates (modulator745) codewords [m+1, n] (the S2S payload (715)) (center bits720) using SSmodgenerating pad symbols as necessary and store all the produced symbols (symbols740). Alternatively, a rate matching mechanism could be used to fill all available symbols in codewords [m+1, n].

Next, in Step635, the transmitting subscriber station concatenates the symbols and transmits.

The BS will demodulate and decode the transmission using SBMCS. Because the BS is using SBMCSto receive the transmission, the data in the SSMCSsection will be received differently than it was transmitted. However, because the S2B MAC header indicates that the message only occupies the first SBbbits of the transmission, no part of the incorrectly demodulated and decoded transmission is processed by the BS.

Calculations of Transmit Durations in Symbols and Bits

The following calculations assume that no rate matching or code puncturing is being employed in order to match the number of bits coded at the SBMCSto the number of available symbols. Instead, it is assumed that code words are designed to produce a number of symbols evenly divisible by the associated modulation.

Before the constant and variable definitions are provided, an explanation must be given as to what is considered a symbol. A symbol is traditionally a time unit only. However, Orthogonal Frequency-Division Multiple Access (OFDMA) provides the ability to transfer multiple modulated constellations within a single symbol time; e.g. each subcarrier is modulated independently and can thus carry a different meaning during each symbol time.

TABLE 1List of constants and their definitionsValueDefinitionSNumber of data symbols in the allocationSBrateCoding rate from subscriber to base (S2B)SBmodNumber of modulated bits per symbol achievable onthe S2B linkSSrateCoding rate from subscriber to subscriber (S2S)SSmodNumber of modulated bits per symbol achievable onthe S2S linkSBHbHeader size (in bits) required in S2B messageSBTbTrailer size (in bits) required in S2B messageULbNumber of uplink message bitsSSHbNumber of bits in S2S headerSBCW—lengthLength, in symbols, of a codeword using SBrateandSBmod

TABLE 2Station-to-base variables, their equations and definitionsVariableEquationDefinitionSBbSBHb+ ULb+ SBTbTotal number of bits in the S2B partof the transmission.SBHsS⁢⁢BHb+U⁢⁢Lb+S⁢⁢BTb+S⁢⁢SHbS⁢⁢Brate×S⁢⁢BmodNumber of symbols, whole and fractional, required to send the composite header containing the required S2B header, uplink message bits and S2S headerCWwhole⌊SS⁢⁢BCW_length⌋Number of whole codewords that fit in an allocation of S symbolsCWH⌈S⁢⁢BHsS⁢⁢BCW_length⌉Number of codewords required to transmit SBHssymbolsSBH—unused(C⁢⁢WH×S⁢⁢BCW_length-S⁢⁢BHs,C⁢⁢WH≤C⁢⁢WwholeS-S⁢⁢BHs,C⁢⁢WH>C⁢⁢WwholeNumber of symbols from the S2B header codewords that are not used by the  header/uplink messages

TABLE 3Station-to-station variables, their equations and definitionsSSSS − (SBHs+ SBH—unused)Number of symbols available fortransmission at the SSMCSSSSB—HbSBH—unused× SBrate× SBmodNumber of bits available in the unusedpart of the S2B leading codewordstransmitted at the SBMCSSSSS—b└SSS× SSrate× SSmod┘Total number of whole bits available tothe S2S payload in the SSMCStransmission part. Here again a floorfunction is required because a fractionalnumber of bits can be generated fromcertain numbers of input symbols. It isassumed that extraneous symbols are padsymbols, that rate matching is employedor that the coder is somehow designed toavoid this issue.SSbSSSB—Hb+ SSSS—bTotal number of whole bits available forthe S2S payload from all parts of thetransmission

FIG. 8illustrates an example of a portion of a wireless communication network800for implementing at least some of the various embodiments discussed previously herein. As illustrated inFIG. 8, the SS pair (SS1805and SS2810) are geographically located close together, while both the SSs (SS1805and SS2810) are geographically remote from the BS815. In this case, it is possible that the BS815would grant a912symbol uplink allocation from SS1805using an MCS of QPSK ½ and an associated codeword length of 128 bits or 128 symbols. In this case, also consider that the link between SS1805and SS2810can sustain an MCS of 64QAM ½.

FIG. 9illustrates a data transmission900for consideration along with the example ofFIG. 8. As illustrated, the example data transmission900includes an 8 byte (64 bits) S2B MAC header905; a 16 bytes (128 bits) of uplink messages910, a 32 bit CRC915and a 1 byte S2S header920.

The SS would need to send the S2B MAC header905, the uplink messages910, the CRC915and the S2S header920all at the SBMCS, a total of 64+128+32+8=224 bits. This means that the first two codewords, or first 256 symbols, need to be transmitted at the SBMCS, though only the first 224 symbols are needed, which leaves 32 symbols for use in transporting S2S data at the SBMCSrate. This also leaves 912−256=656 symbols available for transmission at the SSMCS. Transmitting 656 symbols at the SSMCSprovides an additional 1968 bits to the S2S part. This results in a total of 1968+32=2000 bits available for transporting data between the S2S pair.

Contrast this with sending all data to the BS at the SBMCS. As in the previous example, the transmission must include the S2B MAC header905, the uplink messages910, and a CRC915. It will not, though, require the transmission of an S2S header920. Transporting all data at the SBMCS, then, would provide 896−64−128−32=672 bits of payload. The S2S link provides nearly three times the capacity of the S2B link.

A novel method of using an uplink transmit resource for sending data directly to a peer device has been provided herein. This approach does not require any changes to base station equipment and can be implemented completely in subscriber devices. It allows existing systems to be retrofitted with direct link capabilities without requiring an upgrade to the existing infrastructure. This idea could be used in any system with multi-codeword uplink transmissions where station-to-station links are desired. A good example of such a system is 802.16e.