Patent Description:
Various wireless access technologies have been proposed or implemented to enable mobile stations to perform communications with other mobile stations or with wired terminals coupled to wired networks. Examples of wireless access technologies include GSM (Global System for Mobile communications) or UMTS (Universal Mobile Telecommunications System) technologies, defined by the Third Generation Partnership Project (3GPP); CDMA <NUM> (Code Division Multiple Access <NUM>) technologies, defined by 3GPP2; or other wireless access technologies.

As part of the continuing evolution of wireless access technologies to improve spectral efficiency, to improve services, to lower costs, and so forth, new standards have been proposed. One such new standard is the Long Term Evolution (LTE) standard from 3GPP, which seeks to enhance the UMTS wireless network.

The 3GPP LTE standards have not yet developed efficient space division multiple access (SDMA) solutions. SDMA refers to a technique in which radio frequency (RF) resources (e.g., frequencies, time slots, etc.) can be reused in different geographic regions by transmitting different beams into the different geographic regions using multi- beam antennas. Because of inadequate SDMA solutions in the LTE standards, efficiencies associated with SDMA are not available in conventional LTE wireless networks.

<CIT> discloses a method comprising: including beam identity information into signals transmitted on multiple beams provided by a first station, receiving at a second station signals transmitted from the first station, and identifying beams via which the second station received signals from the first station based on the identity information. At least one beam for transmission on the wireless interface between the stations is then selected.

<CIT> discloses a transmitting apparatus for forming a plurality of transmission beams using a plurality of antennas. Transmission beams having low correlation and high reception quality are selected.

<CIT> discloses a wireless communications system supporting multiple MIMO transmission modes and supporting both diversity and directional transmissions under a plurality of different transmission modes. The system comprises a plurality of transmit and receive antenna elements, wherein the transmit antenna elements are arranged to provide polarization diversity.

<CIT> discloses a communication system employing interference-sensitive mode selection.

<CIT> discloses a method for performance in a wireless communication system using beam-forming transmissions. According to the method, the channel quality is monitored. Channel quality indicators, CQIs, can be used to select a scheduling technique. In addition, the CQI can be used to determine the appropriate beam assignment or to update the beam pattern.

<CIT> discloses a method for obtaining information for use in a smart antenna system. The method includes monitoring an interface between a base station controller and a base station transceiver to receive signalling information being communicated via the interface. The method further includes extracting from the signalling information a subset of the signalling information operable to be used as input for selecting one or more of a plurality of beams for wireless communications.

<CIT> discloses an apparatus for transmitting data in a base station of a wireless communication system, configured to transmit data depending on channel status information feedback from terminals, using a plurality of antennas. Based on the channel status information, a scheduler determines: a terminal to which the base station will transmit data, antennas via which the base station will transmit data among the plurality of antennas, and a space pre-coding method.

According to the present disclosure, there are provided a method, base station and computer readable storage medium according to the attached claims.

In the following description, numerous details are set forth to provide an understanding of some embodiments. However, it will be understood by those skilled in the art that some embodiments may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

<FIG> shows an exemplary wireless network in which a spatial division multiple access (SDMA) mechanism according to preferred embodiments is provided. The wireless network includes a base station <NUM> that includes an antenna array or other assembly (multi-beam antenna) <NUM> for producing multiple beams (spatial beams) <NUM>, <NUM> in a corresponding cell sector <NUM>. Although just two beams <NUM> and <NUM> are depicted in <FIG>, it is noted that more than two beams can be provided in a cell sector in other embodiments. SDMA enables radio frequency (RF) resources (e.g., frequencies, time slots, etc.) to be reused in different geographic regions of a cell sector by transmitting different beams into the different geographic regions using multi-beam antennas. A "beam" (or "spatial beam") refers to a wireless signal (or wireless signals) that is (are) transmitted along a particular geographic path. A beam pattern refers to the coverage area of the beam.

A cell sector is one section of a cell of a cellular network. In alternative implementations, rather than providing multiple beams in a cell sector, it is noted that multiple beams can be provided in a cell. As used here, a "cell segment" can refer to either a cell sector or a cell. To provide SDMA, multiple beams are generated in such a cell segment.

Although just one base station is depicted in <FIG>, it is noted that a wireless network would typically include multiple base stations. In some implementations, the wireless network is a Long Term Evolution (LTE) wireless network as defined by the Third Generation Partnership Project (3GPP). In alternative implementations, other types of wireless networks can be employed. Note that reference to a "LTE wireless network" refers to a wireless network defined by current standards for LTE, or by subsequent standards that evolve from LTE. Moreover, even though reference is made to LTE wireless networks in the ensuing discussion, it is noted that techniques according to preferred embodiments can also be applied to non-LTE wireless networks.

A mobile station <NUM> can communicate using one or both of the beams <NUM>, <NUM> in the cell sector <NUM>, depending upon the position of the mobile station <NUM> in the cell sector. As depicted, the mobile station <NUM> is in a position to communicate using beam <NUM>. The mobile station <NUM> can move to another location in the cell sector <NUM> to communicate using beam <NUM>. Alternatively, the mobile station <NUM> can move to a location that is in an overlap region <NUM> between the beams <NUM> and <NUM>, in which case the mobile station <NUM> is able to communicate using both beams <NUM> and <NUM>.

In an LTE wireless network, the base station <NUM> includes an enhanced node B, which includes a base transceiver station that includes the antenna array <NUM>. The base station <NUM> also includes a radio network controller that cooperates with the enhanced node B. The radio network controller and/or enhanced node B can perform one or more of the following tasks: radio resource management, mobility management for managing mobility of mobile stations, routing of traffic, and so forth. Note that one radio network controller can access multiple node Bs, or alternatively, a node B can be accessed by more than one radio access controller.

As depicted in <FIG>, the base station <NUM> includes one or more central processing units (CPUs) <NUM>, which is (are) connected to storage <NUM>. Moreover, the base station includes software <NUM> that is executable on the CPU(s) <NUM> to perform tasks of the base station <NUM>, including tasks according to preferred embodiments to enable support for SDMA in the LTE wireless network.

The base station <NUM> is connected to a serving and/or packet data network (PDN) gateway <NUM>, which terminates the user plane interface toward the enhanced node B and assumes the responsibility for package routing and transfer towards an external network <NUM>, which can be a packet data network such as the Internet or other type of network.

The arrangement depicted in <FIG> is provided for purposes of example. In other implementations, other wireless network arrangements are used.

In accordance with preferred embodiments, to enable downlink beam selection, the base station <NUM> is able to send different information sets on corresponding beams (e.g., <NUM>, <NUM>) in the cell sector <NUM> for receipt by mobile stations within the cell sector <NUM>. Downlink beam selection refers to selection of one of the beams <NUM>, <NUM> (or both beams <NUM>, <NUM>) depending upon the location of the mobile station to perform communication of downlink data (from the base station <NUM> to the mobile station). The downlink beam selection for a particular mobile station (e.g., <NUM>) is performed at the base station <NUM> in response to indications received from the particular mobile station, where the indications are generated by the particular mobile station depending upon which of the information sets was received by the mobile station.

For example, the mobile station <NUM> located in a region corresponding to beam <NUM> would receive the information set transmitted in beam <NUM>, but will not receive the information set transmitted in beam <NUM>. On the other hand, a mobile station located in a region corresponding to beam <NUM> would receive the information set communicated in beam <NUM>, but would not receive the information set communicated in beam <NUM>. A mobile station located in an overlap region <NUM> between the beams <NUM> and <NUM> would be able to receive both information sets communicated in beams <NUM>, <NUM>.

Depending on the information set(s) detected by the mobile station, the mobile station will send back a corresponding indication to the base station <NUM>. The indication sent by the mobile station will differ depending on which of the information set(s) is detected by the mobile station. Based on the indication received from the mobile station, the base station <NUM> performs beam selection from among plural beams for communicating downlink data to the mobile station. The indication received by the base station <NUM> from the mobile station enables the base station <NUM> to identify the beam that the mobile station is able to receive in the downlink direction.

According to preferred embodiments, the SDMA operation supported by the LTE wireless network is transparent to the mobile station. In other words, changes do not have to be made to mobile stations in the LTE wireless network to provide SDMA support, which reduces costs associated with deploying SDMA. The mobile station is able to detect the information sets communicated by the base station-however, the mobile station does not have to recognize that the information sets were sent in different beams, and the mobile station does not have to be configured to identify which beam the mobile station is communicating with.

In preferred embodiments, the information sets communicated in the beams <NUM>, <NUM> include reference signal structures that contain pilot (reference) signals that are coded according to a predetermined coding scheme. A pilot (reference) signal is a signal that is transmitted by the base station and is used by a mobile station to acquire the wireless network system and to perform other tasks. In some embodiments, the predetermined coding scheme involves the use of a codebook that has a number of entries containing corresponding codewords that can be selectively used for coding the pilot signals in a reference signal structure.

In some implementations, each information set communicated in each of the beams <NUM>, <NUM> includes all pilot signals of the cell sector <NUM>. Thus, for example, if the base station <NUM> transmits two pilot signals in the cell sector <NUM>, then both pilot signals would be communicated in each information set communicated in each corresponding beam <NUM>, <NUM>. However, different codings (using different codewords of the codebook) are applied to the pilot signals in the different information sets, such that a mobile station in a region corresponding to beam <NUM> would receive an information set containing pilot signals subjected to a first coding (using a first codeword), while a mobile station in a region corresponding to beam <NUM> would receive an information set with pilot signals subjected to a second, different coding (using a second codeword).

<FIG> shows an exemplary codebook that has a number of entries containing exemplary codewords. The codebook is arranged as a matrix having rows corresponding to four codebook indexes (<NUM>, <NUM>, <NUM>, <NUM>), and two columns corresponding to two ranks (<NUM>, <NUM>). The arrangement of <FIG> is provided for purposes of example, as the actual data structure of the codebook may be different. There are four entries (containing four respective codewords) corresponding to rank <NUM> and three entries (containing three respective codewords) corresponding to rank <NUM>. "Rank <NUM>" indicates that a particular wireless channel used to communicate data between a base station and a mobile station is able to use two layers, which means that the current RF channel between the base station and the particular mobile station can support two layers (and in a preferred implementation) these two layers will utilize both beams <NUM>, <NUM> simultaneously. This simultaneous transmission of data to the mobile station means that the throughput of data communication is doubled. On the other hand, "rank <NUM>" means that just a single layer can be used for the wireless channel that communicates data between the base station and mobile station. If just a single layer is enabled, then the data transmitted to a mobile station is transmitted in just one of the beams <NUM>, <NUM>. Note that rank <NUM> is possible when a mobile station is located in an overlap region, such as overlap region <NUM>, between multiple beams (e.g., <NUM>, <NUM>).

The entry in the codebook identified by codebook index <NUM> and rank <NUM> has the following value, <MAT>, which means that a first pilot signal and second pilot signal are transmitted in the same positive phase (corresponding to the "+<NUM>" value).

On the other hand, the codeword contained in the entry of the codebook identified by codebook index <NUM> and rank <NUM> has value <MAT>, which means that the first pilot signal has positive phase while the second pilot signal has negative phase (which correspond to the "+<NUM>" and "-<NUM>" values, respectively, of the codeword).

The codeword corresponding to the entry associated with codebook index <NUM> and rank <NUM> has value <MAT>, which means that the first pilot signal has positive phase (corresponding to the "+<NUM>" value), while the second pilot signal is out of phase by <NUM> degrees (corresponding to the "j" value).

The codewords associated with the rank <NUM> entries in the codebook are interpreted similarly, except that the pilot signals subjected to rank <NUM> coding are communicated over two beams, rather than just one beam as with pilot signals subjected to rank <NUM> coding.

<FIG> depict two different information sets, in the form of reference signal structures <NUM> and <NUM>, that are communicated over different beams (e.g., <NUM>, <NUM>). The horizontal axis of each of the reference signal structures <NUM>, <NUM> represent time slots, whereas the vertical axis of each of the reference signal structures <NUM>, <NUM> represent subcarriers (at different frequencies). <FIG> shows a reference signal structure in which the coding applied to pilot signals (represented as R0 and R1) are subjected to coding applied by the codeword contained in the codebook entry corresponding to codebook index <NUM> and rank <NUM>. <FIG> shows a reference signal structure in which the coding applied to pilot signals (represented as R0 and R1) are subjected to coding applied by the codeword contained in the codebook entry corresponding to codebook index <NUM> and rank <NUM>.

The reference signal structures <NUM> and <NUM> differ in that pilot signal R1 in reference signal structure <NUM> has a +<NUM> phase (according to the codeword at codebook index <NUM>, rank <NUM>), while pilot signal R1 in reference signal structure <NUM> has a -<NUM> phase (according to the codeword at codebook index <NUM>, rank <NUM>). The R0 pilot signal occupies the same positions in both reference signal structures <NUM> and <NUM>, and the R0 pilot signal has the same +<NUM> phase in both reference signal structures <NUM>, <NUM>. However, the R1 pilot signals occupy the same positions in the reference signal structures <NUM> and <NUM>, but are out of phase by <NUM>° in the reference signal structures <NUM> and <NUM>.

The indication that is reported by the mobile station back to the base station <NUM> depends upon which reference signal structure is detected by the mobile station. In other words, if a first information set is detected by the mobile station, then a first indication is sent. However, if a second information set is detected by the mobile station, then a second indication is sent. If a combination of the first and second information sets (e.g., reference signal structures corresponding to either beam <NUM> or beam <NUM>) are received by the mobile station, then depending on the relative strength of the two sets, either the beam corresponding to the stronger set will be indicated by the mobile station or if the signals are of comparable strength then a third indication may result that does not correspond to either beam.

In the embodiments, the indication reported by the mobile station is a precoding matrix index (PMI). In an exemplary implementation, a mobile station that is exclusively in a region corresponding to beam <NUM>, with no significant interference from beam <NUM>, will report a first PMI, such as <MAT> which corresponds to the codeword at codebook index <NUM>, rank <NUM>. On the other hand, a mobile station that is located exclusively in beam <NUM> (with no significant interference from beam <NUM>) will report the second PMI, such as <MAT>, which corresponds to the codeword at codebook index <NUM>, rank <NUM>. In some cases, the mobile station can report another rank <NUM> PMI, such as <MAT> or <MAT>. If such other rank <NUM> PMI is reported, then that indicates that the mobile station can see more than one beam. In this scenario, a diversity mode is employed in which the same data is multiplexed using both beams (employing either time diversity, space diversity, block code diversity or some combination of these methods) to the mobile station. In one implementation, the diversity mode used is a spatial frequency block coding (SFBC) mode. A mobile station can see both beams if the mobile station is in an overlap region (e.g., <NUM> in <FIG>) between the two beams.

If the mobile station detects that an RF channel can support two layers, and if the mobile station is in the overlap region (e.g., <NUM>) between two beams, then the mobile station can report a rank <NUM> PMI, such as PMIs corresponding to one of the codewords depicted in the codebook of <FIG>. In such a scenario, the base station will use a MIMO (multiple input multiple output) mode, in which both beams are used for simultaneously communicating different data to the mobile station, to improve throughput.

<FIG> is a message flow diagram of a procedure to perform downlink beam selection by the base station <NUM>. The base station transmits (at <NUM>) reference signal structures in corresponding beams in a given cell sector. Depending on where the mobile station is located, the mobile station can receive one of the beams, or the other of the beams, or both of the beams (assuming that there are two beams). Note that in alternative implementations, more than two beams can be transmitted by the base station.

Based on the reference signal structures detected by the mobile station, the mobile station sends (at <NUM>) a PMI back to the base station <NUM>. Note that the mobile station also sends other information back to the base station, where such other information can include metrics representing beam quality. For example, a metric representing beam quality can be in the form of a channel quality indicator (CQI). The other information transmitted by the mobile station back to the base station includes rank information (e.g., rank <NUM> or rank <NUM>) to indicate the number of layers supported by an RF channel over which the mobile station is communicating. The PMI, CQI, and rank information can be sent by the mobile station to the base station <NUM> in one control message, or in plural control messages. For example, the PMI, CQI, and rank information can be communicated in a physical uplink control channel (PUCCH), or in some other control channel.

Based on the received PMI and other information, the base station <NUM> performs (at <NUM>) downlink beam selection. Beam selection can include the base station selecting one of the beams, or the other of the beams, or both beams, for communicating downlink data with the mobile station. The PMI informs the base station <NUM> the beam(s) that the mobile station is able to see. The CQI information informs the base station <NUM> of the quality of the beam(s) detected by the mobile station, and the rank information informs the base station <NUM> of the number of layers supported by the current RF channel. Using the above information, the base station <NUM> is able to select the beam(s) for use in transmitting downlink data.

Beam selection also involves selecting the mode in which the base station is to communicate downlink data with the mobile station, where the mode can be a single input multiple output (SIMO) mode (in which one beam is used for communicating with each mobile station-note that multiple beams can be used for communicating downlink data to multiple mobile stations). Another mode of operation is a diversity mode, or SFBC mode, in which the same data is sent in multiple beams but in different phases to improve communication performance and cell coverage improvement. Another possible mode is MIMO mode, in which different data is transmitted to a mobile station simultaneously on different beams to improve per-user throughput. Mode selection is also based on the PMI, CQI and rank information.

Note that the beam and mode selection (<NUM>) can be performed by a downlink scheduler (part of software <NUM> in <FIG>) in the base station <NUM>.

Based on the selected mode and beam selection performed at <NUM>, the base station sends (at <NUM>) a downlink scheduling grant message to the mobile station, where the grant message can contain a field to indicate the mode of operation (e.g., MIMO mode, SIMO mode, or SFBC mode). The grant message will also indicate which codeword that the mobile station is to use. For example, the grant message can contain a particular field that can have: (<NUM>) a first value to indicate SIMO mode with a first codeword applied to downlink data sent in the first beam, (<NUM>) a second value to indicate SIMO mode with a second codeword applied to downlink data in the second beam, (<NUM>) a third value to indicate SFBC mode to perform transmit diversity, and (<NUM>) a fourth value to indicate MIMO mode with a corresponding rank <NUM> codeword.

The above has described a technique for enabling the base station <NUM> to (<NUM>) identify, for downlink data communication, the beam that a mobile station is able to receive, and (<NUM>) select the beam(s) that the base station is to use for transmitting downlink data.

In preferred embodiments, to enable the base station to determine which beam the mobile station will be using for uplink data (from the mobile station to the base station <NUM>), the mobile station sends an uplink reference signal. In one example, this uplink reference signal is referred to as a sounding reference signal. As depicted in <FIG>, the mobile station sends (at <NUM>) a sounding reference signal to the base station <NUM>. The base station <NUM> then determines (at <NUM>) whether the mobile station transmitted the sounding reference signal in the first beam or second beam, so that the base station can select the appropriate beam to receive (at <NUM>) uplink data from the mobile station.

The base station <NUM> can include an uplink scheduler (part of software <NUM>) to perform scheduling for communication of uplink data by the mobile stations in the cell sector <NUM>. The uplink scheduler performs the uplink beam selection independently from the downlink scheduler. During handover between different base stations, both the uplink and downlink beam selections have to be considered.

In some exemplary embodiments, downlink control signals can be sent by the base station <NUM> as follows. For example, synchronization signals such as a primary synchronization channel (P-SCH) and secondary synchronization channel (S-SCH) can be sent on both beams <NUM>, <NUM> using a diversity scheme, such as a precoding vector switching (PVS) transmit diversity scheme.

Other downlink control signals can be sent on both beams <NUM>, <NUM> using SFBC diversity transmission. Examples of such other control signals include PCFICH (physical control format indicator channel), PHICH (physical hybrid automatic repeat request indicator channel), and PBCH (physical channel).

Another downlink control channel is the PDCCH (physical downlink control channel). If the number of mobile stations in a cell sector is not large (e.g., less than some predefined threshold), SFBC diversity transmission can be used by the base station <NUM> to send the PDCCH in both beams. However, if there are a relatively large number of mobile stations, the PDCCHs for different mobile stations can be sent in different beams, depending on the locations of the mobile stations. In one example, three groups of mobile stations located in a cell sector can be identified: (<NUM>) group <NUM>: mobile stations in overlap region between two beams; (<NUM>) group <NUM>: mobile stations in first beam area; and (<NUM>) group <NUM>: mobile stations in second beam area. The first beam will be used by the base station <NUM> to transmit PDCCHs to mobile stations in groups <NUM> and <NUM>, while the second beam will be used by the base station <NUM> to transmit PDCCHs to mobile stations in groups <NUM> and <NUM>.

Another downlink control signal that can be sent using SFBC diversity mode is the random access response message that is sent by the base station to the mobile station in response to a random access channel (RACH) from the mobile station. RACH is sent by the mobile station to establish a call or other communications session.

Although reference is made to specific exemplary downlink channels in this discussion, it is noted that different implementations can use different control channels.

In some exemplary embodiments, uplink control signals can be received by the base station <NUM> as follows. The uplink random access channel (RACH) is received by the base station in both beams (so that no beam selection has to be performed). Also, the PUCCH can also be received by the base station in both beams, or the PUCCH can be received in either beam, where users in different beams can be assigned the same PUCCH resources, thus increasing PUCCH capacity (similar to uplink data).

Although reference is made to specific exemplary uplink channels in this discussion, it is noted that different implementations can use different control channels.

In some embodiments, for communication of uplink data or control signaling, two mobile stations are assigned the same resource block (same combination of time slot and subcarrier) in two different beams. For the base station <NUM> to be able to reliably receive the uplink data or control signaling in such a scenario, the base station <NUM> is able to assign two orthogonal demodulation reference signals to the mobile stations. The demodulation reference signal sent by one mobile station will not be shifted; however, the demodulation reference signal sent by the other mobile station will have a half-length cyclic shift applied. The demodulation reference signal and application of cyclic shift is described in the 3GPP <NUM> Specification. The orthogonal demodulation reference signals associated with the uplink data and/or control signaling from the mobile stations will enable the base station <NUM> to accurately detem1ine the mutual RF interference or isolation of the mobile stations in the two beams.

The orthogonal demodulation reference signal to be used by each mobile station for uplink transmission is indicated by the base station in the uplink scheduling grant message. The grant message can include a parameter to indicate the cyclic shift to be applied to the uplink demodulation reference signal for multiuser-MIMO (MU-MIMO) mode. The parameter having a first value indicates no cyclic shift, whereas the parameter having a second value indicates a half length cyclic shift, to provide the orthogonal demodulation reference signals.

Instructions of the software described above, such as software <NUM> in the base station <NUM> of <FIG>, can be executed on a processor. Software can also be executed by a processor in the mobile station <NUM> of <FIG>. The processor includes microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. A "processor" can refer to a single component or to plural components.

Claim 1:
A method at a base station (<NUM>), BS, of providing space division multiple access in a wireless network, comprising:
transmitting a plurality of beams within a cell segment (<NUM>), the plurality of beams including a first beam and a second beam (<NUM>, <NUM>), each of the first beam (<NUM>) and the second beam (<NUM>) defining a respective coverage area of the beam, the respective coverage areas of the first and second beams (<NUM>, <NUM>) overlapping in an overlap region (<NUM>) within the cell segment (<NUM>);
sending (<NUM>) different information sets (<NUM>, <NUM>) in the plurality of beams (<NUM>, <NUM>), wherein one or more of the information sets are detectable by a mobile station (<NUM>) depending upon a location of the mobile station (<NUM>) in the cell segment (<NUM>);
receiving (<NUM>) from the mobile station (<NUM>) in a location within the overlap region (<NUM>):
a first indication responsive to the information sets (<NUM>, <NUM>) in the first and second beams (<NUM>, <NUM>) being detected by the mobile station (<NUM>), wherein receiving the first indication comprises receiving a first Precoding Matrix Index, PMI, and
rank information indicating that a wireless channel between the mobile station (<NUM>) and the base station (<NUM>) can support two layers;
selecting a MIMO mode of transmission based on the received first indication and rank information;
according to the selected MIMO mode of transmission, selecting the first and second beams (<NUM>, <NUM>) from the plurality of beams for simultaneously sending different downlink data from the base station (<NUM>) to the mobile station (<NUM>);
receiving (<NUM>) an uplink reference signal from the mobile station (<NUM>), the uplink reference signal being different than said first indication responsive to the information sets (<NUM>, <NUM>) in the first and second beams (<NUM>, <NUM>) being detected by the mobile station (<NUM>); and
determining (<NUM>) a beam from among the plurality of beams for receiving uplink data from the mobile station (<NUM>) by the base station (<NUM>) based on at least one beam in which the uplink reference signal has been received from the mobile station (<NUM>);
wherein the first and second beams (<NUM>, <NUM>) for sending the downlink data from the base station (<NUM>) to the mobile station (<NUM>) are selected independently of the beam for receiving uplink data from the mobile station (<NUM>) by the base station (<NUM>).