Abstract:
Apparatus for recovering symbols from control and data channels corresponding to a plurality of users is described. Samples corresponding to control channel signals from multiple users are processed on a time shared basis with various control channel processing elements being reused multiple times to processes the samples and recover signals, e.g., symbols, corresponding to the plurality of users. While the control channel processing elements are used on a time shared basis, a separate data channel processing chain or module maybe provided for each of the plurality of users. In some embodiments the order of despreading and filtering is reversed for the control and data channel signal processing.

Description:
RELATED APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Application No. 61/110,533 filed on Oct. 31, 2008, and entitled “COMMUNICATIONS METHODS AND APPARATUS” and which is hereby expressly incorporated by reference in its entirety. 
    
    
     FIELD 
     The present application is directed to communications methods and apparatus, and more particularly, to methods and apparatus which can be used to process uplink signals. 
     BACKGROUND 
     There is a growing interest in the use of small base stations, e.g., femtocells. As the size and number of users supported by a base station diminishes, the cost of the base station can be spread over fewer users. Accordingly, with regard to relatively small base stations, e.g., femtocells, from a commercial implementation perspective keeping hardware costs down becomes important. While keeping hardware costs down is important to commercial success being able to support multiple users at the same time can also be important. 
     In view of the above, it should be appreciated that there is a need for efficiently performing uplink processing, from a hardware prospective, while supporting multiple users. 
     SUMMARY 
     Samples corresponding to control channel signals from multiple users are processed on a time shared basis with various control channel processing elements being reused multiple times to processes the samples and recover signals, e.g., symbols, corresponding to the plurality of users. In some implementations, a control channel despreading module and/or a control channel rake filter module are used on a time shared basis to process a stored set of received samples and recover therefrom control channel input corresponding to different users over time. While the control channel processing elements are used on a time shared basis, a separate data channel processing chain or module  312 ,  322  may, and in some embodiments is provided for each of the plurality of users. 
     The time shared approach to the processing of control channels corresponding to different users while the data channels are processed for the different users individually takes advantage of the relatively low rate of the control channel signalling as compared to the potentially much higher rate of the user data channels. 
     While not required or used in all embodiments, in some embodiments, the order of despreading and filtering is reversed for the control and data channel signal processing. In some, but not necessarily all embodiments, control channel despreading is performed, e.g., by a module  306 , prior to filtering by a filtering module  308 . However, in at least one such embodiment in the case of user data channels filtering is performed by a module, e.g., module  316 , prior to despreading by, e.g., a despreading module  320 . 
     Given that the despreading is the same for different users with regard to the control channel and that despreading reduces the data rate considerably, by placing the filter module  308  after the despreading module  306 , it is possible to operate the filter module at a lower rate than would be required if placed prior to despreading allowing for a lower cost implementation than would be possible if the filtering were performed at the higher data rate prior to despreading. In the case of user data channels however, different despreading may be required for different ones of a user&#39;s multiple data channels. Thus, in the case of user data channel signal processing, in some embodiments it is preferable to perform filtering prior to despreading as shown in the  FIG. 3  embodiment while in the case of the control signals it is easier to implement filtering after the despreading. 
     While the present invention is directed to apparatus such as the one shown in  FIG. 3 , the invention is also directed to methods of signal processing. In various embodiments, the apparatus shown in  FIG. 3  may be used to implement the exemplary methods. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates an exemplary communication system implemented in accordance with one embodiment of the invention. 
         FIG. 2  illustrates an exemplary base station, e.g., access point, implemented in accordance with the invention. 
         FIG. 3  illustrates an exemplary symbol recovery apparatus which can be used in the exemplary base station shown in  FIGS. 1 and 2 , in accordance with one aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a communications system  100  implemented in accordance with one exemplary embodiment of the invention. In the system  100 , multiple wireless terminals, e.g., mobile nodes MN  1  ( 104 ) through MN N ( 106 ) communicate with a base station  102 , e.g., a femtocell, through the use of communication signals  13 ,  15 . While shown as exemplary mobile nodes, the wireless terminal may also include stationary devices. Each mobile terminal may correspond to a different mobile user and are therefore sometimes referred to as user terminals. The signals  13 ,  15  may be, e.g., CDMA or OFDM signals. The base station  102  performs uplink signal processing in accordance with the invention. Thus, signals  13 ,  15  include uplink signals. 
       FIG. 2  illustrates an exemplary base station  200  which may be e.g., an access router, implemented in accordance with the invention. In some embodiments the base station  200  can be used as, e.g., femtocell  102  of system  100 . The base station  200  includes antennas  203 ,  205  and transmitter receiver circuitry  202 ,  204 . The transmitter circuitry  202  includes an encoder  233  while the receiver circuitry  204  includes a decoder  235 . The receiver circuitry  204  further includes a processing module  240  which may be implemented in accordance with the invention, e.g., as shown in  FIG. 3 . The transmitter and receiver circuitry  202 ,  204  is coupled by a bus  230  to an I/O interface  208 , processor (e.g., CPU)  206  and memory  210 . The I/O interface  208  couples the base station  200  to the internet and/or an IP network. The memory  210  includes routines, which when executed by the processor  206 , cause the base station  200  to operate in accordance with the invention. Memory includes communications routines  223  used for controlling the base station  200  to perform various communications operations and implement various communications protocols. The memory  210  also includes a base station/femtocell control routine  225  used to control the base station  200  to implement the steps of the method of the present invention described above. The base station control routine  225  includes a scheduler module  226  used to control transmission scheduling and/or communication resource allocation. Thus, module  226  may serve as a scheduler. Memory  210  also includes information used by communications routines  223 , and control routine  225 . The information  212  includes an entry for each active mobile station user  213 ,  213 ′ which lists the active sessions being conducted by the user and includes information identifying the mobile station (MN) being used by a user to conduct the sessions. 
       FIG. 3  illustrates an exemplary uplink signal processing apparatus  300  which may be used in the receiver of the base station shown in  FIG. 2 . Signals received by antenna  301  are sampled and stored in input replay buffer  302  and also supplied to the input of each of the user data channel processing modules  312 ,  322 . Control channel processing is performed for each N supported users on a time shared basis using control channel despreading module  306  and control channel rake filter module  308 , where N is an integer greater than or equal to 1. In some embodiments N is, e.g., 2, 5, 20 or more. The module  308  optionally includes a diversity combining module  310 . The control module  304  causes the input replay buffer  302  to output a stored set of samples once for each of the N users with the user control channel indicator indicating which of the N users the output of the filter module  308  corresponds to at any given point in time. Note that control channel despreading module  306  precedes the filter module  308  in the  FIG. 3  embodiment. While this is not mandatory, in the illustrated embodiment it allows the filter module  308  to operate at a lower clock rate than the despreading module  306  since the despreading module  306  reduces the sample rate from that output by the input replay buffer  302 . 
     While control channel processing is performed on a time shared basis, user data channel signal processing is performed on a per user basis with a separate data channel processing module, e.g., such as modules  312 ,  322 , being provided for each of the N users. Each data channel processing module  312 ,  322  includes a frame delay unit  314 ,  324 , a data channel filter module  316 ,  326  and a data channel despreading module  320 ,  330 . Note that in at least some embodiments, such as the one shown in  FIG. 3 , the filter module  316 ,  326  precedes the despreading module  320 ,  330 . 
     The filter modules may be optionally implemented as rake filter modules and, depending on the embodiment, may include an optional diversity combining module  318 . 
     The techniques of various embodiments may be implemented using software, hardware and/or a combination of software and hardware. Various embodiments are directed to apparatus, e.g., base stations including one or more attachment points, mobile nodes such as mobile access terminals, and/or communications systems. Various embodiments are also directed to methods, e.g., method of controlling and/or operating mobile nodes, base stations and/or communications systems, e.g., hosts. Various embodiments are also directed to machine, e.g., computer, readable medium, e.g., ROM, RAM, CDs, hard discs, etc., which include machine readable instructions for controlling a machine to implement one or more steps of a method. 
     In some embodiments various features are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a computer readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, various embodiments are directed to a computer readable medium including computer executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s). Some embodiments are directed to a device, e.g., communications device, including a processor configured to implement one, multiple or all of the steps of one or more methods of the invention. 
     Some embodiments are directed to a processor configured to implement one or more of the various functions, steps, acts and/or operations of one or more methods described above. Accordingly, some embodiments are directed to a processor, e.g., CPU, configured to implement some or all of the steps of the methods described herein. The processor may be for use in, e.g., a communications device or other device described in the present application. 
     In some embodiments, the processor or processors, e.g., CPUs, of one or more devices, e.g., communications devices such as base stations are configured to perform the steps of the methods described as being as being performed by the communications device. Accordingly, some but not all embodiments are directed to a device, e.g., communications device, with a processor which includes a module corresponding to each of the steps of the various described methods performed by the device in which the processor is included. In some but not all embodiments a device, e.g., communications device, includes a module corresponding to each of the steps of the various described methods performed by the device in which the processor is included. The modules may be implemented using software and/or hardware. 
     At least some of the methods and apparatus of various embodiments are applicable to a wide range of communications systems including many OFDM as well as non-OFDM and/or non-cellular systems. 
     Numerous additional variations on the methods and apparatus of the various embodiments described above will be apparent to those skilled in the art in view of the above description. Such variations are to be considered within the scope. The methods and apparatus may be, and in various embodiments are, used with CDMA, orthogonal frequency division multiplexing (OFDM), and/or various other types of communications techniques which may be used to provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented as base stations which establish communications links with mobile nodes using OFDM and/or CDMA. In various embodiments the mobile nodes are implemented as notebook computers, personal data assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods.