Abstract:
Multi-user packet detection at multiple mobile stations in a sector may be collectively disabled via a downlink point-to-multipoint command message from a base station. The point-to-multipoint command message may be transmitted on a packet data control channel, typically code division multiplexed, and may be a portion of a QUICKCONFIG message and/or transmitted using less than all of the carrier frequencies used by the base station to transmit downlink packet data. Multi-user packet detection may be subsequently allowed by transmitting a second point-to-multipoint message. The multi-user detection process may comprise checking a portion of a packet against a predetermined list of possible values that indicate the presence of a multi-user packet. The relevant multipoint multi-user packet disable command may be logically ANDed at the mobile station with another mobile station setting based on point-to-point message from the base station to establish the enablement/disablement of the multi-user detection process.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to mobile communication systems; and, more particularly, to methods of handling multi-user packets transmitted on a time shared downlink packet data channel.  
         [0002]     The demand for wireless data services, such as mobile Internet, video streaming, and voice over IP (VoIP), have led to the development of high speed packet data channels to provide high data rates needed for such services. High speed packet data channels are employed on the forward link in a variety of mobile communication systems, including IS-2000 (also known as 1xEV-DV), 1xEV-DO, and Wideband Code Division Multiple Access (WCDMA) systems. The high speed packet data channel is a time shared channel, with downlink transmissions, e.g., from a base station to the mobile stations, time-multiplexed and typically transmitted at full power.  
         [0003]     For many of such systems, the base station may choose whether to transmit a given downlink physical layer data packet to one mobile station or to multiple mobile stations. Typically, this decision is made by a scheduler in the base station based on a number of factors including the presence or absence of queued data, the number of mobile stations, types of services involved, quality of service considerations, and the like. If the base station transmits a multi-user packet, the base station indicates the presence of a multi-user packet, such as by applying one of several pre-defined multi-user preamble MAC indexes reserved for multi-user packets.  
         [0004]     Mobile stations receiving packet transmissions generally avoid decoding the packet if the packet is not intended for them. However, for multi-user packets, the situation is more complicated. For multi-user packets, a given mobile station may have to process the packet to a significant degree in order to see if the packet contains data for it. This involves intense processing on the part of the mobile station, to not only blind rate detect, but to also decode the packet to determine if it contains any relevant data. In contrast, if the base station transmits only “single user” packets, these packets are addressed directly to a specific mobile station via a message preamble, which is simpler to handle. Thus, if the packet is intended for another mobile station, the not-addressed-to mobile stations may quickly and easily detect this and avoid the significant processing load required to blind rate detect and decode the packet.  
         [0005]     Multi-user packets are increasingly utilized in modern wireless communications systems, particularly for handling VoIP traffic. However, if all multi-user packets are required to be processed by a mobile station, including a significant number of multi-user packets not having data for that mobile station, then battery power is wasted. Thus, unnecessary processing multi-user packets by the mobile stations should be avoided.  
         [0006]     Under some existing protocols, the base station may instruct a mobile station to not process multi-user packets on an individual mobile station-by-mobile station basis. This may be accomplished using, for example, an attribute known as MultiUserPacketsEnabled in systems using IS-856 Rev. A protocols. In the IS-856 Rev. A protocols, this attribute is typically negotiated and configured using the so-called Generic Attribute Update Protocol (GUAP). However, having the base station individually contact several mobile stations one-by-one to enable and disable multi-user packet processing is cumbersome, particularly on a dynamic basis.  
         [0007]     Accordingly, there remains a need for alternative approaches to handling multi-user packets on high speed packet data channels.  
       SUMMARY OF THE INVENTION  
       [0008]     Multi-user packet detection processes at multiple mobile stations in a sector may be collectively disabled via a downlink point-to-multipoint command message from a base station. The point-to-multipoint command message may be transmitted on a packet data control channel, typically using code division multiplexing, and may be a portion of a QuickConfig message. The multi-user packet detection process may be subsequently allowed by transmitting a second point-to-multipoint message on the packet data control channel. The point-to-multipoint messages may be transmitted on less than all (e.g., only one) of the carrier frequencies used by the base station to transmit downlink packet data. The multi-user detection process may involve the mobile station checking a portion of a packet against a predetermined list of possible values that indicate the presence of a multi-user packet. The relevant multipoint multi-user packet disable command may be logically ANDed at the mobile station with another mobile station setting based on point-to-point message from the base station to establish the enablement/disablement of the multi-user detection process.  
         [0009]     In one embodiment, the present invention provides a method of operating a base station, the base station operative to transmit multi-user packets on a downlink packet data traffic channel shared by a plurality of mobile stations. The method comprises: collectively disabling a multi-user packet detection process of a plurality of mobile stations by transmitting a first downlink point-to-multipoint command message from a base station to the plurality of mobile stations in a point-to-multipoint fashion. The first downlink point-to-multipoint command message may be transmitted on a packet data control channel, and may be a portion of a QuickConfig message. The disabling the multi-user packet detection process by the plurality of mobile stations may be for a control cycle duration. The process may continue and further comprise subsequently collectively allowing the multi-user packet detection process by the plurality of mobile stations by transmitting a second downlink point-to-multipoint command message from the base station to the plurality of mobile stations in a point-to-multipoint fashion. The plurality of mobile stations may comprise all of the mobile stations in a sector being served by the base station. A corresponding apparatus is also described.  
         [0010]     In another embodiment, a method of operating a mobile station is disclosed that allows a multi-user packet detection process to be disabled based on receipt of a particular message from the base station. The method comprises: receiving a first point-to-multipoint message from a base station; the first message having a command indicator that instructs receiving mobile stations, in response to receiving the command indicator, to disable multi-user packet detection; disabling, at the mobile station, a multi-user packet detection process for one or more subsequently received packets based on said command indicator. The relevant multi-user detection process may comprise checking a portion of a packet against a predetermined list of possible values that indicate the presence of a multi-user packet. The process may continue with subsequently receiving a second point-to-multipoint message from the base station; and, in response to the second message, enabling the multi-user packet detection process. The receiving the first point-to-multipoint message from the base station may comprise receiving the first point-to-multipoint message on a packet data control channel, with the command indicator optionally forming a portion of a Quickconfig message transmitted on the packet data control channel. The multi-user detection process may be disabled for a control channel cycle. The mobile station may set a first attribute to a first logical value in response receiving the first message, with enablement of the multi-user detection process depending on a logical ANDing the first attribute and a second attribute associated with multi-user packets, the second attribute set according to a point-to-point message from the base station. A corresponding apparatus is also described. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  shows an exemplary wireless communication network.  
         [0012]      FIG. 2  shows an exemplary base station.  
         [0013]      FIG. 3  shows an exemplary mobile station.  
         [0014]      FIG. 4  shows a flowchart for a base station operation according to one embodiment of the present invention.  
         [0015]      FIG. 5  shows an exemplary downlink command message.  
         [0016]      FIG. 6  shows a flowchart for a mobile station operation according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     The present invention relates to the handling of multi-user packets transmitted on a downlink packet data channel in a wireless communication system having a plurality of mobile stations operating therein. As such, a brief overview of an exemplary wireless communication system and mobile station may aid in understanding the present invention.  
         [0018]      FIG. 1  illustrates the logical entities of an exemplary wireless communication network  10  that provides packet data services to mobile stations  100 . In general, the wireless communication network  10  may be configured according to the IS-2000 standard, Wideband CDMA (W-CDMA) standard, 1xEV-DO standard, or other standard utilizing multi-user downlink packets. Thus, the wireless communication network  10  is a packet-switched network that employs a high-speed forward packet data channel (F-PDCH) to transmit data to the mobile stations  100 . Wireless communication network  10  includes a packet-switched core network  20  and a radio access network (RAN)  30 . The core network  20  includes a Packet Data Serving Node (PDSN)  22  that connects to an external packet data network (PDN)  16 , such as the Internet, and supports PPP connections to and from the mobile stations  100 . Core network  20  adds and removes IP streams to and from the RAN  30  and routes packets between the external packet data network  16  and the RAN  30 .  
         [0019]     RAN  30  connects to the core network  20  and gives mobile stations  100  access to the core network  20 . RAN  30  includes a Packet Control Function (PCF)  32 , one or more base station controllers (BSCs)  34  and one or more radio base stations (RBSs)  36 . The primary function of the PCF  32  is to establish, maintain, and terminate connections to the PDSN  22 . The BSCs  34  manage radio resources within their respective coverage areas. The RBSs  36  include the radio equipment for communicating over the air interface with mobile stations  100 . A BSC  34  can manage more than one RBSs  36 . In cdma2000 networks, a BSC  34  and an RBS  36  comprise a base station  40 . The BSC  34  is the control part of the base station  40 . The RBS  36  is the part of the base station  40  that includes the radio equipment and is normally associated with a cell site. In cdma2000 networks, a single BSC  34  may function as the control part of multiple base stations  40 . In other network architectures, the network components comprising the base station  40  may be different, but the overall functionality will be the same or similar.  
         [0020]      FIG. 2  illustrates exemplary details of a base station  40  in a cdma2000 network. The base station components in the exemplary embodiment are distributed between a RBS  36  and a BSC  34 . The RBS  36  includes RF circuits  42 , baseband processing and control circuits  44 , and interface circuits  46  for communicating with the BSC  34 . The RF circuits  42  include one or more transmitters  42 T and receivers  42 R, which transmit signals to, and receive signals from, the mobile stations  100 . For example, the receiver  42 T receives the channel quality indicators (CQIs) reported by the mobile stations  100  and passes the same on to the baseband processing and control circuits  44  for processing. The baseband processing and control circuits  44  perform baseband processing of transmitted and received signals. In the embodiment shown in  FIG. 2 , the baseband processing and control circuit  44  includes a scheduler  60  to schedule packet data transmissions on the Forward Packet Data Channel (F-PDCH). The scheduler  60  makes scheduling decisions and selects the appropriate modulation and coding schemes based on, inter alia, channel feedback from the mobile stations  100 . The baseband processing and control circuit  44 , including the scheduler  60 , may be implemented as one or more processing circuits, comprising hardware, software, or any combination thereof, that are configured as appropriate to implement one or more of the processes described herein. For example, the baseband processing and control circuit  44  may be implemented as stored program instructions executed by one or more microprocessors or other logic circuits included in RBS  36 .  
         [0021]     The BSC  34  includes interface circuits  50  for communicating with the RBS  36 , communication control circuits  52 , and interface circuits  54  for communicating with PCF  32 . The communication control circuits  52  manage the radio and communication resources used by the base station  40 . The communication control circuits  52  are responsible for setting up, maintaining and tearing down communication channels between the RBS  36  and mobile station  100 . The communication control circuits  52  may also allocate Walsh codes and perform power control functions. The communication control circuits  52  may be implemented in software, hardware, or some combination of both. For example, the communication control circuits  52  may be implemented as stored program instructions executed by one or more microprocessors or other logic circuits included in BSC  34 .  
         [0022]      FIG. 3  illustrates details of an exemplary mobile station  100 . The mobile station  100  includes an RF section  110 , baseband processing and control circuits  120 , memory  130 , user interface  140 , audio circuits  150 , and an application processor  160 . RF section  110  provides a radio interface for communicating with base stations  40 . The RF section  110  includes a transmitter  112  and receiver  114  coupled to a shared antenna  118  through an RF switch  116 . Transmitter  112  modulates transmitted signals onto an RF carrier and amplifies the transmit signal for transmission. Receiver  114  filters, amplifies, and downconverts received signals to baseband for processing by the baseband processing and control circuits  120 . The baseband processing and control circuits  120  perform baseband processing for signals transmitted from, and received by, the mobile station, and control the overall operation of the mobile station  100 . The baseband processing and control circuits  120  may comprise one or more processors, hardware, firmware, or a combination thereof. The baseband processing and control circuits  120  include a signaling processor  122  that performs signaling tasks required by applicable standards, such as rate control signaling.  
         [0023]     Memory  130  stores programs and data used by the baseband processing and control circuits  120  and application processor  160 . Memory  130  may take the form of one or more memory devices and may include both random access memory (RAM) and read-only memory (ROM). Computer programs and data required for operation of the device are typically stored in non-volatile memory, such as EPROM, EEPROM, and/or flash memory. The memory devices may be implemented as discrete devices, stacked devices, or integrated with processors in the baseband processing and control circuits  120 .  
         [0024]     User interface  140  typically includes one or more input devices  142  and one or more displays  144 . The input devices  142  typically take the form of a keypad, joy stick control, touch pad, dial, and/or any other known type of input device. Display  144  typically takes the form of a conventional LCD, but may alternatively take the form of a touch screen display that also serves as an input device  142 .  
         [0025]     Audio circuits  150  include audio processing circuits  152 , microphone  154 , and speaker  156 . Audio processing circuits  152  include D-to-A converters to convert digitized audio to analog signals suitable for output to speaker  156 , and analog-to-digital converters for converting analog input signals from microphone  154  to digitized audio suitable for input to the baseband processing and control circuits  120 . Microphone  154  converts the user&#39;s speech and other audible signals into electrical audio signals, and speaker  156  converts analog audio signals into audible signals that can be heard by the user.  
         [0026]     Application processor  160  runs installed user applications, such as personal information management (PIM) applications, email applications, and instant messaging applications, as is well known in the art.  
         [0027]      FIG. 4  illustrates a process flow for a base station according to one embodiment of the present invention. As is customary, the scheduler  60  determines if it is appropriate to send multi-user packets on the downlink packet data channel (step  210 ). If multi-user packets are to be transmitted (step  220 ), the baseband processing and control circuits  44  prepare a command message  290  (step  230 ) that includes an indication  296  that multi-user packet processing may be enabled at the mobile stations  100 . If no multi-user packets are to be transmitted (step  220 ), the baseband processing and control circuits  44  prepare a command message  290  (step  240 ) that includes an indication  296  that multi-user packet processing is to be disabled at the mobile stations  100 . Either way, the command message is then transmitted in a point-to-multipoint fashion (PTM) to all the mobile stations  100  in a sector being served by that base station  40  (step  250 ). Typically, this is accomplished by transmitting the command message on the packet data control channel (PDCCH). The relevant packets are then transmitted on the downlink packet data (traffic) channel (step  260 ), and the process begins again. Thus, the base station  40  transmits the multi-user packet processing enable/disable indicator to the mobile stations  100  each control channel cycle.  
         [0028]     The multi-user packet processing enable/disable indicator may, in some embodiments, be a simple one-bit flag in the command message  290 , with a value of “0” indicating multi-user packet detection is to be disabled and a value of “1” indicating that multi-user packet detection is to be allowed. For example, a one-bit field  296  may be added to the existing QUICKCONFIG message field  294  in the current IS-856 Rev. A standard. The resulting command message  290  may be as shown in  FIG. 5 , with the indicator  296  appended to the balance of the QUICKCONFIG message  294 , which is bundled with the other portions  292  of the command message  290 . For ease of reference, this multi-user packet processing enable/disable indicator  296  discussed immediately above may be referred to herein as a multipoint multi-user packet command (MMUP command)  296 .  
         [0029]     From the perspective of the mobile station  100 , the sector-wide MMUP command  296  may be view as an augmentation to any existing settings related to multi-user packets. For example, the MMUP command  296  may be logically ANDed with the MultiUserPacketsEnabled attribute to determine if the mobile station  100  will process multi-user packets. Thus, if both the MMUP command  296  and the MultiUserPacketsEnabled attribute indicate that the mobile station  100  should process multi-user packets, then the mobile station  100  processes the multi-user packets (e.g., blind rate detects and decode them) to see if they contain any data intended for the mobile station  100 . On the other hand, if either the MultiUserPacketsEnabled attribute or the MMUP command  296  (or both) indicate that the mobile station  100  should not process multi-user packets, then the mobile station  100  may ignore any packets not targeted only at that mobile station, including any multi-user packets, as soon as they are identified.  
         [0030]     As is understood, a multi-user packet is typically identified by the presence of one of a few (e.g., five) selected MAC indexes in the packet preamble, while a single-user packet is indicated by a MAC index assigned to the targeted mobile station. Thus, a mobile station  100  that has been commanded to ignore multi-user packets, due to the MMUP command or the MultiUserPacketsEnabled attribute, need only determine if the packet preamble has a single known MAC index—the one corresponding to the MAC expected by the mobile station  100  based on its channel feedback information. If so, the packet should be further processed, if not, the packet may be disregarded. In contrast, a mobile station  100  that has multi-user packet processing enabled must determine if a given packet has that MAC index or any of the multi-user MAC indexes. Therefore, having the multi-user packet processing disabled is less computationally complex, and therefore consumes less battery power.  
         [0031]      FIG. 6  illustrates a process flow for a mobile station  100  according to one embodiment of the present invention. The mobile station  100  is configured by the base station  40  on an individual basis via the GAUP process for the MultiUserPacketsEnabled attribute (step  304 ). In the absence of an explicit setting, the mobile station  100  may have a default of not enabled. The mobile station  100  also receives the MMUP command  296  from the base station  40  on the packet data control channel (step  306 ) in a PTM message. The mobile station  100  logically ANDs these two settings to determine whether multi-user packet processing is enabled for the current control channel cycle (step  308 ). Somewhat separately, the mobile station  100  receives the packets on the downlink packet data (traffic) channel (step  310 ). The mobile station  100  checks to see if the MAC index in the preamble matches the MAC index for that mobile station (step  320 ) in a fashion known in the art. If the MAC index matches, the packet is a “single-user” packet and intended for that mobile station. As such, the packet is passed on for further conventional processing (step  360 ). If the MAC index does not match, the mobile station  100  checks to see if multi-user processing is enabled (step  330 ). If not, because one or both of the MultiUserPacketsEnabled attribute of the MMUP command are negative, the mobile station  100  disregards the packet and moves on to the next packet (step  390 ). If multi-user packet processing is enabled, then the mobile station  100  checks the MAC index against a list of pre-determined MAC indexes that are reserved for indicating the present of multi-user packets (step  340 ). If the MAC index is not on that list, the packet is not a multi-user packet; if the MAC index is on that list, then the packet is a multi-user packet. If the packet is a multi-user packet (step  350 ), the packet passed on for further processing to see if the packet contains data for that mobile station (step  360 ). If the packet is not a multi-user packet (step  350 ), the packet is disregarded and the mobile station  100  moves on to the next packet (step  390 ).  
         [0032]     The ability of the base station  40  to send a PTM command that disables multi-user packet processing for multiple mobile stations  100  in a sector with a single command transmission greatly increases the flexibility of the base stations  40  to dynamically respond to changing situations, without the burden of having to instruct each mobile station  100  individually. Further, the present invention allows the base station  40  to enable multi-user packet processing in individual mobile stations  100  via GAUP process, but temporarily disable the functionality via the MMUP command  296  (set to disable) when multi-user packets are not being transmitted.  
         [0033]     The discussion above has indicated that the MMUP command  296  is transmitted from the base station  40  to the mobile terminals  100  in a point-to-multipoint (PTM) fashion, i.e., where the MMUP command  296  is simultaneously transmitted from a single source (the base station  40 ) to multiple users (multiple mobile stations  100 ) over a common channel. It should be noted that this PTM transmission may be a “broadcast” or a “multicast,” as is desired. A distinction is sometimes drawn between broadcasting and multicasting. The distinction is that a broadcast stream is typically offered to all users in a sector, while a multicast stream is offered to a special multicast group of two or more users. Broadcast and multicast services are both PTM (point-to-multipoint) transmissions. Thus, if it is desired to disable multi-user packet detection in all the mobile stations  100  in a sector (i.e., being served by the base station  40 ), the base station  40  may transmit the MMUP command  296  as a broadcast message. This scheme is believed advantageous. However, in some instances, it may be beneficial to disable the multi-user packet detection in only a select group of such mobile stations  100 . For such situations, the base station  40  may transmit the MMUP command  296  as a multicast message to the multicast group that contains the relevant mobile stations  100 .  
         [0034]     The discussion above has been assumed that the base station  40  has a single carrier frequency for downlink packet data transmissions. However, some base stations  40  may transmit downlink packets to mobile stations on multiple carrier frequencies. For such situations, the MMUP command  296  may indicate whether multi-user packet detection is to be disabled or allowed separately for each carrier frequency. Thus, the MMUP command  296  may be multi-bit command, with each bit representing the disable/allowed state for the corresponding carrier frequency. For such situations, it may be advantageous for the base station  40  to transmit the MMUP command  296  as part of control messages on an anchor carrier frequency, if one of the multiple carrier frequencies is designated as such.  
         [0035]     As used herein, the term “mobile station”  40  may include a cellular radiotelephone, a Personal Communications System (PCS) terminal that may combine a cellular radiotelephone with data processing, facsimile, and data communications capabilities; a Personal Data Assistant (PDA) that may include a pager, Web browser, radiotelephone, Internet/intranet access, organizer, calendar, and a conventional laptop and/or palmtop receiver or other appliances that include a radiotelephone transceiver.  
         [0036]     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.