Patent Application
20060227737
The following description relates to communication systems and in particular to wireless communication systems.
Many changes are taking place in the way wireless communication networks are being deployed. Some of the changes are being driven by the adoption of new mobile communications standards. The introduction of software defined radios to wireless telecommunications has led to the generation of software and hardware solutions to meet the new standards. Current mobile communication standards introduce physical and logical channels and pose new issues in the transport of information within the communication networks.
A software defined radio (SDR) uses software for the modulation and demodulation of radio signals. The use of reprogrammable software allows key radio parameters, such as frequency and modulation protocols to be modified without the need to alter the underlying hardware of the system. Additionally, SDRs allow a single device to support multiple configurations which previously would have required multiple hardware devices. One example of a software defined radio is the Vanu Software Radio produced by Vanu, Inc. (See U.S. Pat. No. 6,654,428).
Some modulation standards that wireless communication networks operate with include, but are not limited to, Advanced Mobile Phone System (AMPS), code division multiple access (CDMA), Wide-band CDMA (WCDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), Cellular Digital Packet Data (CDPD), Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), Integrated Digital Enhanced Network (iDEN), and Orthogonal Frequency Division Multiplexing (OFDM).
In standards that implement digital processing of voice and data communications, data streams typically carry digital samples of the voice and data communications in the form of digital words of a finite bit length and multiplex into a single data stream digital words comprising voice and data communications for several end users of the communications network. Often, a plurality of digital words is bundled together into groups to increase the processing efficiency of communications network systems. Because of this, various network systems must maintain synchronization to ensure agreement about which digital words in a data stream belong to the same group. Because of the various modulation standards currently in use for wireless networks, purchasing network system components designed to operate with only a single modulation standard results in idle resources at times when network demand for that modulation standard is low.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art today for methods and systems that maintain data stream synchronization that are modulation standard independent.
Embodiments of the present invention address the problem of maintaining network synchronization, as well as other problems and will be understood by reading and studying the following specification.
In one embodiment, a communications system is provided. The system comprises one or more radio head interface modules and a call processing software module, the one or more radio head interface modules adapted to communicate with the call processing software module. The call processing software module performs modulation and demodulation of voice and data streams using one or more air interface standards. The call processing software module communicates a forward data stream to a first radio head interface of the one or more radio head interface modules. The forward data stream comprises a plurality of data samples representing voice and data streams and a plurality of fixed synchronization words. When the first radio head interface module does not observe the receipt of a first fixed synchronization word of the plurality of fixed synchronization words word from the call processing software module when expected, the first radio head interface module concludes that it has lost synchronization with the call processing software module.
In another embodiment, a method of page resynchronization is provided. The method comprises: communicating a data stream between a radio head interface module and a call processing software module, wherein the data stream comprises a plurality of data samples representing voice and data streams and a plurality of fixed synchronization words; observing the receipt of a first fixed synchronization word of the plurality of fixed synchronization words at an expected position within the data stream; and when the first fixed synchronization word does not occur when expected on a first logical channel, concluding that a loss of synchronization has occurred on the first logical channel between the radio head interface module and the call processing software module.
In yet another embodiment, a computer-readable medium having computer-executable instructions for page resynchronization is provided. The method comprises: communicating a data stream between a radio head interface module and a call processing software module, wherein the data stream comprises a plurality of data samples representing voice and data streams and a plurality of fixed synchronization words; observing the receipt of a first fixed synchronization word of the plurality of fixed synchronization words at an expected position within the data stream; and when the first fixed synchronization word does not occur when expected on a first logical channel, concluding that a loss of synchronization has occurred on the first logical channel between the radio head interface module and the call processing software module.
In still yet another embodiment a communications system is disclosed. The system comprises one or more radio head interface modules, means for modulating and demodulating voice and data streams using one or more air interface standards, means for communicating a forward data stream to a first radio head interface module of the one or more radio head interface modules, wherein the forward data stream comprises a plurality of data samples representing voice and data streams and a plurality of fixed synchronization words. The first radio head interface module including means for observing the receipt of a first fixed synchronization word of the plurality of fixed synchronization words sent from the means for modulating and demodulating voice and data streams at an expected position, means to stop processing the forward data stream when the first fixed synchronization word is not observed at the expected position, means to observe a second fixed synchronization word sent from the means for modulating and demodulating voice and data streams, and means to resume processing of the forward data stream upon observation of the second fixed synchronization word.
The present invention is more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present invention. Reference characters denote like elements throughout the figures and text.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.
Embodiments of the present invention provide methods and systems to maintain synchronization, detect loss of synchronization, and perform resynchronization of reconfigurable network hardware for mobile communications systems.
Embodiments of the present invention concern portions of a cellular telecommunications network that typically comprises one or more cellular antennas, a radio head unit transmitting and receiving voice and/or data communications over the cellular antennas, and a base station (also commonly called a base transceiver station (BTS), or a server) that communicates data between the radio head unit and a larger communication network (e.g. the public switched telephone network, or the Internet). One or more base stations are connected to a base station controller (BSC) which controls data communication flow in one or more connected base stations.
In some embodiments, communications between a BTS and a radio head unit take place through two sets of data streams. Typically, forward logical channels carry data from the BTS through the radio head unit to an end user device. Reverse logical channels carry data from end user devices through the radio head unit to the BTS. Each of the data streams is assigned a radio frequency (RF) channel and a modulation protocol, which the radio head unit uses to wirelessly communicate data with individual cellular devices.
In some embodiments, additional reverse links are also provided for duplicate reverse logical channels. In some embodiments, this set of duplicate reverse logical channels are called diversity channels. It should be understood that descriptions in this specification relating to embodiments of reverse logical channels also apply to such diversity channels. Further details pertaining to diversity channel are provided in the '676 application incorporated herein by reference.
In one embodiment, BTS 110 communicates with radio head unit 104 through a radio head interface module 106 (or radio head interface 106). Radio head interface 106 establishes high speed digital communication paths for two or more sets of base band data stream logical channels and all communication between BTS 110 and radio head unit 104 goes through radio head interface 106. Radio head interface module 106, radio head unit 104, and call processing software module 114, all handle multiple types of modulation protocols, and in different embodiments, one or more of the logical channels transmit data using a different modulation protocol than another logical channel. In one embodiment, radio head interface module 106, radio head unit 104, and call processing software module 114, handle modulation protocols for one or more of, but not limited to, Advanced Mobile Phone System (AMPS), code division multiple access (CDMA), Wide-band CDMA (WCDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), Cellular Digital Packet Data (CDPD), Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), Integrated Digital Enhanced Network (iDEN), Orthogonal Frequency Division Multiplexing (OFDM), or any other appropriate modulation protocol. A modulation protocol is commonly also referred to as an air interface standard, a modulation standard, an air interface protocol, or an air interface modulation protocol. For each logical channel, BTS 110 performs modulation and demodulation of forward and reverse logical channel voice and data streams using one or more of the air interface standard protocols. In one embodiment, the forward and reverse logical channel data streams carry complex RF data samples representing digital voice and data communications.
In one embodiment, radio head interface module 106 is coupled to BTS 110 through an interface device 116. In one embodiment, interface device 116 is one of, but not limited to a PCI-X interface, an ATCA interface, a PCI Express interface, a Gigabit Ethernet interface, a SCSI interface, a Rocket I/O interface, a UDP/IP link interface, a TCP/IP link interface, a Serial ATA interface, a Card bus for PCMIA card interface, a high speed serial interface or a high speed parallel interface.
In one embodiment, in the forward link, call processing software module 114 compiles voice and data information from communication networks 120 into collections of complex RF data samples. In one embodiment the collection of complex RF data samples forms a page of complex RF data samples wherein each page contains data samples for one forward logical channel.
In one embodiment, each page of complex RF data samples further comprises a page header generated by call processing software 114. In one embodiment, the page header comprises two digital quadwords that prefix the complex RF data samples. In one embodiment, the page of complex RF data samples includes 256 quadwords, each quadword having two complex RF data samples. In one embodiment, each quadword is 64 bits long. Although embodiments of the present invention are illustrated using pages having 258 quadwords of 64 bits in length (i.e. each page having 2 quadwords of page header plus 256 quadwords of complex RF data samples), it will be understood by those in the art that embodiments of the present invention apply to any finite length page containing digital data and embodiments are not limited by the bit lengths or formatting of digital words comprising the RF data samples.
A loss of synchronization between call processing software 114 and radio head interface module 106 is illustrated by the following example. In the embodiment described in the above paragraph each page (page header and complex RF data samples together) is 258 quadwords in length. If a data stream ever drops a quadword or repeats a quadword, then synchronization is lost because call processing software 114 and radio head interface module 106 will no longer agree on which set of 258 consecutive quadwords comprise a single page. The radio head interface module and the call processing software are no longer in agreement concerning page boundaries and quadwords containing complex RF data samples can be confused as page headers and vise-versa.
Embodiments of the present invention utilize a fixed synchronization word located at a defined position within a page header as a reference to identify the boundaries of a page. In one embodiment, the fixed synchronization word is a start of page indicator (PSI) located within the first quadword of a page header. Referring to
Embodiments of the present invention provide the following advantages: 1) loss of synchronization detection is automatic, 2) loss of synchronization detection time is fast—occurring within one page of the loss of synchronization, 3) resynchronization is automatic, 4) resynchronization is fast—occurring within one page of when the loss of synchronization is detected, and 5) as will be illustrated below, forward and reverse path detection and resynchronization are independent.
To detect a loss of synchronization in the reverse link, embodiments of the present invention utilize a fixed synchronization word located at a defined position within a reverse page header as a reference to identify the boundaries of a page. In one embodiment, the fixed synchronization word is a PSI located within the first quadword of a reverse link page header.
Several ways are available to implement the radio head interface module and server elements of the current invention. These include, but are not limited to, digital computer systems, programmable controllers, or field programmable gate arrays. Therefore other embodiments of the present invention are the program instructions resident on computer readable media which when implemented by such controllers, enable the controllers to implement embodiments of the present invention. Computer readable media include any form of computer memory, including but not limited to punch cards, magnetic disk or tape, any optical data storage system, flash ROM, non-volatile ROM, PROM, E-PROM or RAM, or any other form of permanent, semi-permanent, or temporary memory storage system or device.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
This application is related to the following co-pending U.S. patent applications filed on even date herewith, all of which are hereby incorporated herein by reference: U.S. patent application Ser. No. ______ (attorney docket number 100.672US01 entitled “DYNAMIC FREQUENCY HOPPING”) and which is referred to here as the '672 application; U.S. patent application Ser. No. ______ (attorney docket number 100.673US01 entitled “DYNAMIC DIGITAL UP AND DOWN CONVERTERS”) and which is referred to here as the '673 application; U.S. patent application Ser. No. ______ (attorney docket number 100.675US01 entitled “DYNAMIC RECONFIGURATION OF RESOURCES THROUGH PAGE HEADERS”) and which is referred to here as the '675 application; U.S. patent application Ser. No. ______ (attorney docket number 100.676US01 entitled “SIGNAL ENHANCEMENT THROUGH DIVERSITY”) and which is referred to here as the '676 application; U.S. patent application Ser. No. ______ (attorney docket number 100.677US01 entitled “SNMP MANAGEMENT IN A SOFTWARE DEFINED RADIO”) and which is referred to here as the '677 application; U.S. patent application Ser. No. ______ (attorney docket number 100.678US01 entitled “TIME STAMP IN THE REVERSE PATH”) and which is referred to here as the '678 application; U.S. patent application Ser. No. ______ (attorney docket number 100.679US01 entitled “BUFFERS HANDLING MULTIPLE PROTOCOLS”) and which is referred to here as the '679 application; U.S. patent application Ser. No. ______ (attorney docket number 100.680US01 entitled “TIME START IN THE FORWARD PATH”) and which is referred to here as the '680 application; U.S. patent application Ser. No. ______ (attorney docket number 100.684US01, entitled “DYNAMIC REALLOCATION OF BANDWIDTH AND MODULATION PROTOCOLS” and which is referred to here as the '684 application; U.S. patent application Ser. No. ______ (attorney docket number 100.685US01 entitled “DYNAMIC READJUSTMENT OF POWER”) and which is referred to here as the '685 application; U.S. patent application Ser. No. ______ (attorney docket number 100.686US01 entitled “METHODS AND SYSTEMS FOR HANDLING UNDERFLOW AND OVERFLOW IN A SOFTWARE DEFINED RADIO”) and which is referred to here as the '686 application; and U.S. patent application Ser. No. ______ (attorney docket number 100.700US01 entitled “INTEGRATED NETWORK MANAGEMENT OF A SOFTWARE DEFINED RADIO SYSTEM”) and which is referred to here as the '700 application.
