WO2015024213A1

WO2015024213A1 - Enhanced gsm cell acquisition

Info

Publication number: WO2015024213A1
Application number: PCT/CN2013/081948
Authority: WO
Inventors: Mungal Singh Dhanda; Philip J. Children; Simon Walke; Damon M. Beales; Jiming Guo
Original assignee: Qualcomm Incorporated
Priority date: 2013-08-21
Filing date: 2013-08-21
Publication date: 2015-02-26
Also published as: WO2015024366A1

Abstract

A method for wireless communication is described. The method includes beginning acquisition. An acquisition scan of ARFCNs for supported bands in an adjustable scan list is performed. A home PLMN is identified from a SIM card. A possible list of PLMNs expected in the region is identified. It is determined whether all expected PLMNs in the list of PLMNs expected in the region were found during the acquisition scan. It is also determined whether the home PLMN was found during the acquisition scan.

Description

ENHANCED GSM CELL ACQUISITION

TECHNICAL FIELD

[0001] The present disclosure relates generally to communication systems. More specifically, the present disclosure relates to systems and methods for enhanced Global System for Mobile Communications (GSM) cell acquisition.

BACKGROUND

[0002] Wireless communication systems have become an important means by which many people worldwide have come to communicate. A wireless communication system may provide communication for a number of wireless communication devices, each of which may be serviced by a base station.

[0003] Users of wireless communication devices desire that their devices have many features. For example, a user may expect to power on a wireless communication device and immediately make or receive a phone call. But, wireless communication devices must perform initial acquisition and camp on procedures before service can be obtained and wireless communications can be established. Those procedures may need to be performed at power on and whenever a wireless communication device leaves a service area and then returns to a service area. These procedures may require considerable amounts of time before a user can make a phone call. Benefits may be realized by decreasing the amount of time needed for acquisition and camp on procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 shows a wireless communication system with multiple wireless devices according to some embodiments;

[0005] Figure 2 shows an example of a wireless communication system according to some embodiments;

[0006] Figure 3 shows a block diagram of a transmitter and a receiver in a wireless communication system according to some embodiments;

[0007] Figure 4 shows a block diagram of a design of a receiver unit and demodulator at a receiver according to some embodiments;

[0008] Figure 5 shows example frame and burst formats in GSM according to some embodiments; [0009] Figure 6 shows an example spectrum in a GSM system according to some embodiments;

[0010] Figure 7 illustrates an example of a wireless device that includes transmit circuitry (including a power amplifier), receive circuitry, a power controller, a decode processor, a processing unit for use in processing signals and memory according to some embodiments;

[0011] Figure 8 illustrates an example of a transmitter structure and/or process according to some embodiments;

[0012] Figure 9 is a flow diagram of a method for enhanced GSM cell acquisition according to some embodiments;

[0013] Figure 10 is a flow diagram of another method for enhanced GSM cell acquisition according to some embodiments;

[0014] Figure 11 is a flow diagram of a method for maintaining a PLMN database;

[0015] Figure 12 is a flow diagram of a method for updating the PLMN database;

[0016] Figure 13 illustrates an ARFCN multiframe according to some embodiments; and

[0017] Figure 14 illustrates certain components that may be included within a wireless communication device according to some embodiments.

DETAILED DESCRIPTION

[0018] Figure 1 shows a wireless communication system 100 with multiple wireless devices according to some embodiments. Wireless communication systems 100 are widely deployed to provide various types of communication content such as voice, data and so on. A wireless device may be a base station 102 or a wireless communication device 104. The wireless communication device may be configured for enhanced GSM cell acquisition. For example, the wireless communication device may be configured to dynamically adjust the list of cells that are searched for available public land mobile networks (PLMNs).

[0019] A base station 102 is a station that communicates with one or more wireless communication devices 104. A base station 102 may also be referred to as, and may include some or all of the functionality of, an access point, base transceiver station (BTS), a broadcast transmitter, a NodeB, an evolved NodeB, etc. The term "base station" will be used herein. Each base station 102 provides communication coverage for a particular geographic area. A base station 102 may provide communication coverage for one or more wireless communication devices 104. The term "cell" can refer to a base station 102 and/or its coverage area depending on the context in which the term is used.

[0020] Communications in a wireless communication system 100 (e.g., a multiple- access system) may be achieved through transmissions over a wireless link. Such a communication link may be established via a single-input and single-output (SISO), multiple-input and single-output (MISO) or a multiple-input and multiple-output (MIMO) system. A MIMO system includes transmitter(s)and receiver(s)equipped, respectively, with multiple (Νχ) transmit antennas and multiple (N_R) receive antennas for data transmission. SISO and MISO systems are particular instances of a MIMO system. The MIMO system can provide improved performance (e.g., higher throughput, greater capacity or improved reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.

[0021] The wireless communication system 100 may utilize MIMO. A MIMO system may support both time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, uplink and downlink transmissions are in the same frequency region so that the reciprocity principle allows the estimation of the downlink channel from the uplink channel. This enables a transmitting wireless device to extract transmit beamforming gain from communications received by the transmitting wireless device.

[0022] The wireless communication system 100 may be a multiple-access system capable of supporting communication with multiple wireless communication devices 104 by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, wideband code division multiple access (W-CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single- carrier frequency division multiple access (SC-FDMA) systems, 3^rd Generation Partnership Project (3 GPP) Long Term Evolution (LTE) systems and spatial division multiple access (SDMA) systems.

[0023] The terms "networks" and "systems" are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes W-CDMA and Low Chip Rate (LCR) while cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) .An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDMA, etc. UTRA, E-UTRA and GSM are part of Universal Mobile Telecommunication System (UMTS).Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA.UTRA, E-UTRA, GSM, UMTS and Long Term Evolution (LTE) are described in documents from an organization named "3rd Generation Partnership Project" (3GPP).cdma2000 is described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2).

[0024] The 3^rd Generation Partnership Project (3 GPP) is a collaboration between groups of telecommunications associations that aims to define a globally applicable 3^rd generation (3G) mobile phone specification.3GPP Long Term Evolution (LTE) is a 3 GPP project aimed at improving the Universal Mobile Telecommunications System (UMTS) mobile phone standard. The 3GPP may define specifications for the next generation of mobile networks, mobile systems and mobile devices.

[0025] In 3GPP Long Term Evolution (LTE), a wireless communication device 104 may be referred to as a "user equipment" (UE).A wireless communication device 104 may also be referred to as, and may include some or all of the functionality of, a terminal, an access terminal, a subscriber unit, a station, etc. A wireless communication device 104may be a cellular phone, a personal digital assistant (PDA), a wireless device, a wireless modem, a handheld device, a laptop computer, etc.

[0026] A wireless communication device 104 may communicate with zero, one or multiple base stations 102 on the downlink 129 and/or uplink 127 at any given moment. The downlink 129 (or forward link) refers to the communication link from a base station 102 to a wireless communication device 104, and the uplink 127 (or reverse link) refers to the communication link from a wireless communication device 104 to a base station 102. A wireless communication device 104 may be configured to use Global System for Mobile Communications (GSM), Long Term Evolution (LTE), wireless fidelity (Wi-Fi) and wideband CDMA.

[0027] The Global System for Mobile Communications (GSM) is a widespread standard in cellular, wireless communication. GSM is relatively efficient for standard voice services. However, high-fidelity audio and data services require higher data throughput rates than that for which GSM is optimized. To increase capacity, the General Packet Radio Service (GPRS), EDGE (Enhanced Data rates for GSM Evolution) and UMTS (Universal Mobile Telecommunications System) standards have been adopted in GSM systems. In the GSM/EDGE Radio Access Network (GERAN) specification, GPRS and EGPRS provide data services. The standards for GERAN are maintained by the 3 GPP (Third Generation Partnership Project). GERAN is a part of GSM. More specifically, GERAN is the radio part of GSM/EDGE together with the network that joins the base stations 102 (the Ater and Abis interfaces) and the base station controllers (A interfaces, etc.). GERAN represents the core of a GSM network. It routes phone calls and packet data from and to the PSTN (Public Switched Telephone Network) and Internet to and from remote terminals. GERAN is also a part of combined UMTS/GSM networks.

[0028] GSM employs a combination of Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) for the purpose of sharing the spectrum resource. GSM networks typically operate in a number of frequency bands. For example, a GSM network may use the GSM-850 band, the EGSM band (also referred to as the E-GSM-900 band), the DCS (digital cellular service) band (also referred to as DCS-1800), the PCS (personal communications service) band (also referred to as PCS- 1900), the P-GSM band, the R-GSM band and the T-GSM band. Due to refarming, many additional GSM bands may also be employed that have not yet been defined.

[0029] The GSM-850 band commonly may use a radio spectrum in the 824.2-849.2 megahertz (MHz) frequency range for uplink 127 and the 869.2-894.2 MHz frequency range for downlink 129. The EGSM band may use a radio spectrum in the 880-915 MHz frequency range for uplink 127 and the 925-960 MHz frequency range for downlink 129. The DCS band may use a radio spectrum in the 1710.2-1784.8 MHz frequency range for uplink 127 and the 1805.2-1879.8 MHz frequency range for downlink 129. The PCS band may use a radio spectrum in the 1850.2-1909.8 MHz frequency range for uplink 127 and the 1930.2-1989.8 MHz frequency range for downlink 129.

[0030] Furthermore, each frequency band may be divided into 200 kilohertz (kHz) carrier frequencies providing a number of RF channels spaced at 200 kHz. The number of channels may not be the same for each band.GSM-1900 uses the 1850-1910 MHz bands for the uplink 127 and 1930-1990 MHz bands for the downlink 129. Like GSM 900, FDMA divides the spectrum for both uplink 127 and downlink 129 into 200 kHz- wide carrier frequencies. Similarly, GSM-850 uses the 824-849 MHz bands for the uplink 127 and 869-894 MHz bands for the downlink 129, while GSM- 1800 uses the 1710-1785 MHz bands for the uplink 127 and 1805-1880 MHz bands for the downlink 129.

[0031] Each channel in GSM is identified by a specific absolute radio frequency channel number (ARFCN).For example, ARFCN 1 - 124 are assigned to the channels of GSM-900, ARFCN 128 - 251 are assigned to the channels of GSM-850, ARFCN 0 - 124 and 955 - 1023are assigned to EGSM, ARFCN 512 - 885 are assigned to DCS and ARFCNs 512-810 are assigned to PCS. Although the PCS band and the DCS band shared some common ARFCNs, the shared ARFCNs are mapped to different carrier frequencies (and in general, the PCS band and the DCS band do not co-exist).In GSM, each channel may have a channel width of 200 kHz. Thus, the EGSM band has 173 channels, the DCS band has 374 channels, the PCS band has 299 channels and the GSM-850 band has 124 channels.

[0032] GSM frequencies for each GSM band (including the EGSM band) and the corresponding number of ARFCNs are given in Table 1 :

Table 1

[0033] Of this list, most GSM mobile stations support four GSM bands: 850, 900, 1800 and 1900. In different parts of the world, different combinations of these four bands may be deployed. For example, in Europe and Asia GSM 900 and 1800 are used while GSM 850 and 1900 are used in North America and GSM 850, 1800 and 1900 are used in Latin America. Networks are free to use any of the ARFCNs from the supported bands for broadcast channels. When a wireless communication device searches for available PLMNs, the wireless communication device must first search for which ARFCNs are carrying the broadcast control channel (BCCH).

[0034] Finding which ARFCNs are carrying the BCCH may involve measuring the power level on all ARFCNs of all supported bands and then attempting synchronization on each ARFCN with a power level higher than the sensitivity of the wireless communication device. However, not every ARFCN with a good power level carries the BCCH. For example, some ARFCNs may carry traffic data. In addition, other mobile technologies (such as CDMA, WCDMA and LTE) may use the same bands as GSM. The wireless communication device may detect an ARFCN with a good power level that is being used by another technology and the wireless communication device is then unable to decode the synchronization channel.

[0035] Searching for available PLMNs on a large number of ARFCNs can take a long time. This is especially true if there are other mobile technologies using the same band. In response, wireless communication devices may employ scan lists. A scan list may include a limited number of ARFCNs (sometimes referred to as a truncated list). For example, a scan list may include the thirty ARFCNs with the highest power for GSM 850, the thirty ARFCNs with the highest power for GSM 900, the forty ARFCNs with the highest power for GSM 1800 and the forty ARFCNs with the highest power for GSM 1900. The wireless communication device may attempt synchronization only on the number of ARFCNs in the scan list when searching for available PLMNs, thereby reducing the time spent searching ARFCNs with low power.

[0036] The wireless communication device 104 may include an enhanced GSM cell acquisition module 105. The enhanced GSM cell acquisition module 105 may decrease the amount of time required for the wireless communication device 104 to register with a subscribed network.

[0037] Typically, scan lists have not been adjustable. By using an adjustable scan list (i.e., a scan list with an adjustable number of ARFCNs), benefits may be realized. For example, using scan lists that are too small may result in valid PLMNs not being visible in the cell selection process. Furthermore, a user of the wireless communication device may not get a complete list of available PLMNs in the region/area. Using scan lists that are too large may take excessive amounts of time.

[0038] In one configuration, the wireless communication device may include a SIM card. The wireless communication device may only search for available PLMNs when a valid SIM card is inserted. A valid SIM card may include the PLMN ID of the home PLMN. Thus, when the wireless communication device searches all the ARFCNs in the adjustable scan list and the home PLMN is not found, the wireless communication device may extend the length of the adjustable scan list until the wireless communication device finds the home PLMN or until all available cells have been searched. This ensures that the user will be shown their own operator, even if the PLMN falls outside the number of ARFCNs that the wireless communication device searches. It may improve user experience to ensure that the wireless communication device always finds the home PLMN.

[0039] The wireless communication device may also include a PLMN database. The PLMN database may list all the PLMNs available for an area/region. For example, different available references list all the PLMNs in each country, which could be used as a baseline. When the wireless communication device is searching for all available PLMNs, the wireless communication device can search until all the PLMNS which are known to be available in the area are found or until all the ARFCNs in the adjustable scan list have been searched. In other words, if all the PLMNs available have already been found, the wireless communication device may stop scanning the ARFCNs in the adjustable scan list. In one configuration, the use of the PLMN database may allow the wireless communication device to stop the search much earlier than scanning every ARFCN in the adjustable scan list (leading to a better response time).

[0040] As the number of networks deployed could change over time, the wireless communication device may periodically (e.g., once per month) update the PLMN database by performing a full search and then adding PLMNs that have become available to the PLMN database and deleting PLMNs that have not been found for a number of full searches (e.g., PLMNs that are no longer operational).

[0041] Scanning the ARFCNs allows the wireless communication device 104 to determine the possible cells that can act as the serving cell. Specifically, the wireless communication device 104 may scan the ARFCNs to find a frequency correction channel (FCCH) 113. The FCCH 113 is a downlink-only control channel in the GSM Um air interface 131 that enables the wireless communication device 104 to lock a local oscillator (LO) to the base station 102 clock. The FCCH 113 is transmitted in frames immediately before the synchronization channel (SCH).Thus, once a wireless communication device 104 has found the FCCH 113, the wireless communication device 104 can then find and decode the SCH.

[0042] Figure 2 shows an example of a wireless communication system 200 according to some embodiments. The wireless communication system 200 includes multiple base stations 202 and multiple wireless communication devices 204. Each base station 202 provides communication coverage for a particular geographic area 206.

[0043] To improve system capacity, a base station coverage area 206 may be partitioned into plural smaller areas, e.g., three smaller areas 208a, 208b, and 208c.Each smaller area 208a, 208b, 208c may be served by a respective base transceiver station (BTS).The term "sector" can refer to a BTS and/or its coverage area 208 depending on the context in which the term is used. For a sectorized cell, the BTSs for all sectors of that cell are typically co-located within the base station 202 for the cell.

[0044] Wireless communication devices 204 are typically dispersed throughout the wireless communication system 200. For a centralized architecture, a system controller 210 may couple to the base stations 202 and provide coordination and control for the base stations 202. The system controller 210 may be a single network entity or a collection of network entities. As another example, for a distributed architecture, base stations 202 may communicate with one another as needed.

[0045] Figure 3 shows a block diagram of a transmitter 371 and a receiver 373 in a wireless communication system according to some embodiments. For the downlink 129, the transmitter 371 may be part of a base station 102 and the receiver 373 may be part of a wireless communication device 104. For the uplink 127, the transmitter 371 may be part of a wireless communication device 104 and the receiver 373 may be part of a base station 102.

[0046] At the transmitter 371, a transmit (TX) data processor 375 receives and processes (e.g., formats, encodes, and interleaves) data 330 and provides coded data. A modulator 312 performs modulation on the coded data and provides a modulated signal. The modulator 312 may perform Gaussian minimum shift keying (GMSK) for GSM, 8- ary phase shift keying (8-PSK) for Enhanced Data rates for Global Evolution (EDGE), etc. GMSK is a continuous phase modulation protocol whereas 8-PSK is a digital modulation protocol. A transmitter unit (TMTR) 318 conditions (e.g., filters, amplifies, and upconverts) the modulated signal and generates an RF modulated signal, which is transmitted via an antenna 320. [0047] At the receiver 373, an antenna 322 receives RF modulated signals from the transmitter 371 and other transmitters. The antenna 322 provides a received RF signal to a receiver unit (RCVR) 324. The receiver unit 324 conditions (e.g., filters, amplifies, and downconverts) the received RF signal, digitizes the conditioned signal, and provides samples. A demodulator 326 processes the samples as described below and provides demodulated data 332.A receive (RX) data processor 328 processes (e.g., deinterleaves and decodes) the demodulated data and provides decoded data. In general, the processing by demodulator 326 and RX data processor 328 is complementary to the processing by the modulator 312 and the TX data processor 375, respectively, at the transmitter 371.

[0048] Controllers/processors 314 and 334 direct operation at the transmitter 371 and receiver 373, respectively. Memories 316 and 336 store program codes in the form of computer software and data used by the transmitter 371 and receiver 373, respectively.

[0049] Figure 4 shows a block diagram of a design of a receiver unit 424 and a demodulator 426 at a receiver 373 according to some embodiments. Within the receiver unit 424, a receive chain 427 processes the received RF signal and provides I (inphase) and Q (quadrature) baseband signals, which are denoted as I_bb and Q_bb- The receive chain 427 may perform low noise amplification, analog filtering, quadrature downconversion, etc. as desired or needed. An analog-to-digital converter (ADC) 428 digitalizes the I and Q baseband signals at a sampling rate of fade from a sampling clock 429 and provides I and Q samples, which are denoted as I_adc and Q_adc. In general, the ADC sampling rate fade may be related to the symbol rate f_ym by any integer or non- integer factor.

[0050] Within the demodulator 426, a pre -processor 430 performs pre-processing on the I and Q samples from the analog-to-digital converter (ADC) 428. For example, the pre-processor 430 may remove direct current (DC) offset, remove frequency offset, etc. An input filter 432 filters the samples from the pre-processor 430 based on a particular frequency response and provides input I and Q samples, which are denoted as Ii_n and Qi_n. The input filter 432 may filter the I and Q samples to suppress images resulting from the sampling by the analog-to-digital converter (ADC) 428 as well as jammers. The input filter 432 may also perform sample rate conversion, e.g., from 24X oversampling down to 2X oversampling. A data filter 433 filters the input I and Q samples from the input filter 432 based on another frequency response and provides output I and Q samples, which are denoted as I_out and Q_out. The input filter 432 and the data filter 433 may be implemented with finite impulse response (FIR) filters, infinite impulse response (IIR) filters, or filters of other types. The frequency responses of the input filter 432 and the data filter 433 may be selected to achieve good performance. In one design, the frequency response of the input filter 432 is fixed and the frequency response of the data filter 433 is configurable.

[0051] An adjacent-channel-interference (ACI) detector 434 receives the input I and Q samples from the input filter 432, detects for adjacent-channel-interference (ACI) in the received RF signal, and provides an adjacent-channel-interference (ACI) indicator 436 to the data filter 433. The adjacent-channel-interference (ACI) indicator 436 may indicate whether or not adjacent-channel-interference (ACI) is present and, if present, whether the adjacent-channel-interference (ACI) is due to the higher RF channel centered at +200 kilohertz (kHz) and/or the lower RF channel centered at -200 kHz. The frequency response of the data filter 433 may be adjusted based on the adjacent- channel-interference (ACI) indicator 436, to achieve desirable performance.

[0052] An equalizer/detector 435 receives the output I and Q samples from the data filter 433 and performs equalization, matched filtering, detection and/or other processing on these samples. For example, the equalizer/detector 435 may implement a maximum likelihood sequence estimator (MLSE) that determines a sequence of symbols that is most likely to have been transmitted given a sequence of I and Q samples and a channel estimate.

[0053] Figure 5 shows example frame and burst formats in GSM according to some embodiments. The timeline for transmission is divided into multiframes 537. For traffic channels used to transmit user- specific data, each multiframe 537 in this example includes 26 TDMA frames 538, which are labeled as TDMA frames 0 through 25. The traffic channels are sent in TDMA frames 0 through 11 and TDMA frames 13 through 24 of each multiframe 537. A control channel is sent in TDMA frame 12. No data is sent in idle TDMA frame 25, which is used by the wireless communication devices 104 to make measurements of signals transmitted by neighbor base stations 102.

[0054] Each time slot within a frame is also referred to as a "burst" 539 in GSM. Each burst 539 includes two tail fields, two data fields, a training sequence (or midamble) field and a guard period (GP).The number of symbols in each field is shown inside the parentheses. A burst 539 includes symbols for the tail, data, and midamble fields. No symbols are sent in the guard period. TDMA frames of a particular carrier frequency are numbered and formed in groups of 26 or 51 TDMA frames 538 called multiframes 537.

[0055] Also, each base station 102 is assigned one or more carrier frequencies. Each carrier frequency is divided into eight time slots (which are labeled as time slots 0 through 7) using TDMA such that eight consecutive time slots form one TDMA frame with a duration of 4.615 milliseconds (ms). A physical channel occupies one time slot within a TDMA frame. Each active wireless communication device 104 or user is assigned one or more time slot indices for the duration of a call. User-specific data for each wireless communication device 104 is sent in the time slot(s) assigned to that wireless communication device 104 and in TDMA frames used for the traffic channels.

[0056] Figure 6 shows an example spectrum 600 in a GSM system according to some embodiments. In this example, five RF modulated signals are transmitted on five RF channels that are spaced apart by 200 kHz. The RF channel of interest is shown with a center frequency of 0 Hz. The two adjacent RF channels have center frequencies that are +200 kHz and -200 kHz from the center frequency of the desired RF channel. The next two nearest RF channels (which are referred to as blockers or non-adjacent RF channels) have center frequencies that are +400 kHz and -400 kHz from the center frequency of the desired RF channel. There may be other RF channels in the spectrum 600, which are not shown in Figure 6 for simplicity. In GSM, an RF modulated signal is generated with a symbol rate of f_Sy_m = 13000/ 40 = 270.8 kilo symbols/second (ksps) and has a -3 decibel (dB) bandwidth of up to 135 kHz. The RF modulated signals on adjacent RF channels may thus overlap one another at the edges, as shown in Figure 6.

[0057] In GSM/EDGE, frequency bursts (FB) are sent regularly by the base station 102. This allows wireless communication devices 104 to synchronize their local oscillator (LO) to the base station 102 local oscillator (LO), using frequency offset estimation and correction. These bursts comprise a single tone, which corresponds to all "0" payload and training sequence. The all zero payload of the frequency burst is a constant frequency signal, or a single tone burst. When in acquisition, the wireless communication device 104 hunts continuously for a frequency burst from a list of carriers. Upon detecting a frequency burst, the wireless communication device 104 will estimate the frequency offset relative to its nominal frequency, which is 67.7 kHz from the carrier. The wireless communication device 104 local oscillator (LO) will be corrected using this estimated frequency offset. In power up mode, the frequency offset can be as much as +/-19 kHz. The wireless communication device 104 will periodically wakeup to monitor the frequency burst to maintain its synchronization in standby mode. In the standby mode, the frequency offset is within ± 2 kHz.

[0058] One or more modulation schemes are used in GERAN systems to communicate information such as voice, data, and/or control information. Examples of the modulation schemes may include GMSK (Gaussian Minimum Shift Keying), M-ary QAM (Quadrature Amplitude Modulation) or M-ary PSK (Phase Shift Keying), where M=2ⁿ, with n being the number of bits encoded within a symbol period for a specified modulation scheme. GMSK is a constant envelope binary modulation scheme allowing raw transmission at a maximum rate of 270.83 kilobits per second (Kbps).

[0059] General Packet Radio Service (GPRS) is a non-voice service. It allows information to be sent and received across a mobile telephone network. It supplements Circuit Switched Data (CSD) and Short Message Service (SMS). GPRS employs the same modulation schemes as GSM. GPRS allows for an entire frame (all eight time slots) to be used by a single mobile station at the same time. Thus, higher data throughput rates are achievable.

[0060] The EDGE standard uses both the GMSK modulation and 8-PSK modulation. Also, the modulation type can be changed from burst to burst. 8-PSK modulation in EDGE is a linear, 8-level phase modulation with 3π/8 rotation, while GMSK is a nonlinear, Gaussian-pulse-shaped frequency modulation. However, the specific GMSK modulation used in GSM can be approximated with a linear modulation (i.e., 2-level phase modulation with a π/2 rotation). The symbol pulse of the approximated GSMK and the symbol pulse of 8-PSK are identical. The EGPRS2 standard uses GMSK, QPSK, 8-PSK, 16-QAM and 32-QAM modulations. The modulation type can be changed from burst to burst. Q-PSK, 8-PSK, 16-QAM and 32-QAM modulations in EGPRS2 are linear, 4-level, 8-level, 16-level and 32-level phase modulations with 3π/4, 3π/8, π/4, - π/4 rotation, while GMSK is a non-linear, Gaussian-pulse-shaped frequency modulation. However, the specific GMSK modulation used in GSM can be approximated with a linear modulation (i.e., 2-level phase modulation with a π/2 rotation). The symbol pulse of the approximated GSMK and the symbol pulse of 8-PSK are identical. The symbol pulse of Q-PSK, 16-QAM and 32-QAM can use spectrally narrow or wide pulse shapes.

[0061] Figure 7 illustrates an example of a wireless device 700 that includes transmit circuitry 741 (including a power amplifier 742), receive circuitry 743, a power controller 744, a decode processor 745, a processing unit 746 for use in processing signals and memory 747 according to some embodiments. The wireless device 700 may be a base station 102 or a wireless communication device 104. The transmit circuitry 741 and the receive circuitry 743 may allow transmission and reception of data, such as audio communications, between the wireless device 700 and a remote location. The transmit circuitry 741 and receive circuitry 743 may be coupled to an antenna 740.

[0062] The processing unit 746 controls operation of the wireless device 700. The processing unit 746 may also be referred to as a central processing unit (CPU). Memory 747, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processing unit 746. A portion of the memory 747 may also include non- volatile random access memory (NVRAM).

[0063] The various components of the wireless device 700 are coupled together by a bus system 749 which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus. For the sake of clarity, the various busses are illustrated in Figure 7 as the bus system 749.

[0064] The steps of the methods discussed may also be stored as instructions in the form of software or firmware located in memory 747 in a wireless device 700. These instructions may be executed by the controller/processor(s) 210 of the wireless device 700. Alternatively, or in conjunction, the steps of the methods discussed may be stored as instructions in the form of software or firmware 748 located in memory 747 in the wireless device 700. These instructions may be executed by the processing unit 746 of the wireless device 700 in Figure 7.

[0065] Figure 8 illustrates an example of a transmitter structure and/or process according to some embodiments. The transmitter structure and/or process of Figure 8 may be implemented in a wireless device such as a wireless communication device 104 or a base station 102. The functions and components shown in Figure 8 may be implemented by software, hardware or a combination of software and hardware. Other functions may be added to Figure 8 in addition to or instead of the functions shown.

[0066] In Figure 8, a data source 850 provides data d(t) 851 to a frame quality indicator (FQI)/encoder 852. The frame quality indicator (FQI)/encoder 852 may append a frame quality indicator (FQI) such as a cyclic redundancy check (CRC) to the data d(t).The frame quality indicator (FQI)/encoder 852 may further encode the data and frame quality indicator (FQI) using one or more coding schemes to provide encoded symbols 853.Each coding scheme may include one or more types of coding, e.g., convolutional coding, Turbo coding, block coding, repetition coding, other types of coding or no coding at all. Other coding schemes may include automatic repeat request (ARQ), hybrid ARQ (H-ARQ) and incremental redundancy repeat techniques. Different types of data may be encoded with different coding schemes.

[0067] An interleaver 854 interleaves the encoded data symbols 853 in time to combat fading and generates symbols 855. The interleaved symbols 855 may be mapped by a frame format block 856 to a pre-defined frame format to produce a frame 857.1n an example, a frame format block 856 may specify the frame 857 as being composed of a plurality of sub-segments. Sub-segments may be any successive portions of a frame 857 along a given dimension, e.g., time, frequency, code or any other dimension. A frame 857 may be composed of a fixed plurality of such sub-segments, each sub-segment containing a portion of the total number of symbols allocated to the frame. In one example, the interleaved symbols 855 are segmented into a plurality S of sub-segments making up a frame 857.

[0068] A frame format block 856 may further specify the inclusion of, e.g., control symbols (not shown) along with the interleaved symbols 855. Such control symbols may include, e.g., power control symbols, frame format information symbols, etc.

[0069] A modulator 858 modulates the frame 857 to generate modulated data 859. Examples of modulation techniques include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK).The modulator 858 may also repeat a sequence of modulated data.

[0070] A baseband-to-radio-frequency (RF) conversion block 860 may convert the modulated data 859 to RF signals for transmission via an antenna 861 as a signal 862 over a wireless communication link to one or more wireless device receivers.

[0071] Figure 9 is a flow diagram of a method 900 for enhanced GSM cell acquisition according to some embodiments. The method 900 may be performed by a wireless communication device 104. In one configuration, the wireless communication device 104 may be configured according to GSM standards. [0072] The wireless device may perform a power scan on supported bands to create a power scan list. The wireless communication device may select a default number of cells with the highest power level from each supported band and store these cells in an acquisition list. The wireless communication device may then perform an acquisition on an ARFCN in the acquisition list. Although not required, the wireless communication device may perform the acquisition on the ARFCN in the acquisition list with the highest detected power level.

[0073] The wireless communication device may then determine whether all the PLMNs that were expected in the region have been found. For example, the wireless communication device may determine whether all the PLMNs available for the area/region in the PLMN database have been found. If all the PLMNs available for the area/region in the PLMN database have been found, the wireless communication device may stop the acquisition.

[0074] If all the PLMNs that were expected in the region have not been found, the wireless communication device may determine whether the acquisition list has been exhausted (i.e., whether an acquisition has been performed on every ARFCN in the acquisition list). If the acquisition list has not been exhausted, the wireless communication device may perform an acquisition on the next ARFCN in the acquisition list.

[0075] If the acquisition list has been exhausted, the wireless communication device may determine whether the home PLMN has been found. For example, the wireless communication device may know the home PLMN ID from a SIM card. If the home PLMN has been found, the wireless communication device may stop the acquisition. If the home PLMN has not been found, the wireless communication device may determine whether the power scan list has been exhausted. If the power scan list has not been exhausted (i.e., there are additional ARFCNs that were found during the power scan list that acquisition has not been performed on), the wireless communication device may extend the acquisition list by adding more cells from the power scan list. The wireless communication device may then perform an acquisition on the next ARFCN in the acquisition list. If the power scan list has been exhausted, the wireless communication device may stop the acquisition.

[0076] Figure 10 is a flow diagram of another method 900 for enhanced GSM cell acquisition according to some embodiments. The method 900 may be performed by a wireless communication device 104. In one configuration, the wireless communication device 104 may be configured according to GSM standards.

[0077] The wireless device may perform a power scan. The power scan may quickly find all the available ARFCNs. The wireless communication device may then begin acquisition. The wireless communication device may perform an acquisition scan of the ARFCNs for supported bands in an adjustable scan list. Thus, the wireless communication device may only perform the acquisition scan for ARFCNs that were discovered during the power scan and that are currently in the adjustable scan list.

[0078] The wireless communication device may determine whether the home PLMN (which is identified in the SIM card) was found during the acquisition scan. If the home PLMN was found during the acquisition scan, the wireless communication device may stop performing further acquisition. In one configuration, the wireless communication device may also decrease the number of ARFCNs in the adjustable scan list.

[0079] If the home PLMN was not found during the acquisition scan, the wireless communication device may determine whether all available cells have been searched. If all available cells have been searched, the wireless communication device may stop performing further acquisition. If all available cells have not been searched, the wireless communication device may increase the number of ARFCNs in the adjustable scan list. The wireless communication device may then continue the acquisition scan. Thus, the acquisition scan may be extended. The wireless communication device may again determine whether the home PLMN has been found after continuing the acquisition scan.

[0080] Figure 11 is a flow diagram of a method for maintaining a PLMN database. The method may be performed by a wireless communication device. The wireless communication device may maintain a PLMN database of PLMNs available for an area/region. In one configuration, the wireless communication device may receive the PLMN database over the network. The wireless communication device may identify the known PLMNs that should be available for the area/region (from the PLMN database). The wireless communication device may perform a power scan to obtain all the ARFCNs. The wireless communication device may begin acquisition.

[0081] The wireless communication device may perform an acquisition scan of the ARFCNs for supported bands in an adjustable scan list. As the acquisition scan is being performed, the wireless communication device may determine whether all the known PLMNs have been found. If all the known PLMNs have been found, the wireless communication device may stop the acquisition scan (even if the acquisition scan has not scanned all the ARFCNs in the adjustable scan list). Thus, the wireless communication device does not have to waste time scanning ARFCNs if all the known PLMNs have already been found.

[0082] If all the known PLMNs have not been found, the wireless communication device may determine whether all the cells in the adjustable scan list have been scanned. If all the cells in the adjustable scan list have been scanned, the wireless communication device may update the PLMN database. Updating the PLMN database is discussed in additional detail below in relation to Figure 12.

[0083] If less than all the cells in the adjustable scan list have been scanned, the wireless communication device may continue performing the acquisition scan for supported bands in the adjustable scan list.

[0084] Figure 12 is a flow diagram of a method for updating the PLMN database. The method may be performed by a wireless communication device. The method may be performed periodically (e.g., every 30 days during the middle of the night). The wireless communication device may begin updating the PLMN database. The wireless communication device may perform a full search to update the PLMN database. The full search may include scanning every available ARFCN to search for available PLMNs. The wireless communication device may add newly found PLMNs to the PLMN database. The wireless communication device may also remove PLMNs from the PLMN database that have not been found for a number of searches (e.g., after three full searches without being found). In this way, the PLMN database may be kept up to date.

[0085] Figure 13 illustrates an ARFCN multiframe 1170 according to some embodiments. The ARFCN multiframe 1170 may be from a scanned ARFCN 111 that is determined to include a frequency correction channel (FCCH) 1171. Because the ARFCN multiframe 1170 includes a frequency correction channel (FCCH) 1171, the ARFCN multiframe 1170 also includes a synchronization channel (SCH) 1172 that immediately follows the frequency correction channel (FCCH) 1171. The ARFCN multiframe 1170 may also include other information, such as the broadcast control channel (BCCH), the common control channel (CCCH) and the stand-alone dedicated control channel (SDCCH).

[0086] Figure 14 illustrates certain components that may be included within a wireless communication device 1304 according to some embodiments. The wireless communication device 1304may be an access terminal, a mobile station, a user equipment (UE), etc. The wireless communication device 1304 includes a processor 1303. The processor 1303 may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor 1303 may be referred to as a central processing unit (CPU). Although just a single processor 1303 is shown in the wireless communication device 1304 of Figure 14, in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used.

[0087] The wireless communication device 1304 also includes memory 1305. The memory 1305 may be any electronic component capable of storing electronic information. The memory 1305 may be embodied as random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers and so forth, including combinations thereof.

[0088] Data 1307a and instructions 1309a may be stored in the memory 1305. The instructions 1309a may be executable by the processor 1303 to implement the methods disclosed herein. Executing the instructions 1309a may involve the use of the data 1307a that is stored in the memory 1305.When the processor 1303 executes the instructions 1309, various portions of the instructions 1309b may be loaded onto the processor 1303, and various pieces of data 1307b may be loaded onto the processor 1303.

[0089] The wireless communication device 1304 may also include a transmitter 1311 and a receiver 1313 to allow transmission and reception of signals to and from the wireless communication device 1304 via an antenna 1317. The transmitter 1311 and receiver 1313 may be collectively referred to as a transceiver 1315. The wireless communication device 1304 may also include (not shown) multiple transmitters, multiple antennas, multiple receivers and/or multiple transceivers.

[0090] The wireless communication device 1304 may include a digital signal processor (DSP) 1321. The wireless communication device 1304 may also include a communications interface 1323. The communications interface 1323 may allow a user to interact with the wireless communication device 1304.

[0091] The various components of the wireless communication device 1304 may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in Figure 14 as a bus system 1319.

[0092] The techniques described herein may be used for various communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, and so forth. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub- carriers. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub- carrier may be independently modulated with data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub- carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub- carriers. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA.

[0093] In the above description, reference numbers have sometimes been used in connection with various terms. Where a term is used in connection with a reference number, this is meant to refer to a specific element that is shown in one or more of the Figures. Where a term is used without a reference number, this is meant to refer generally to the term without limitation to any particular Figure.

[0094] The term "determining" encompasses a wide variety of actions and, therefore, "determining" can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, "determining" can include resolving, selecting, choosing, establishing and the like. [0095] The phrase "based on" does not mean "based only on," unless expressly specified otherwise. In other words, the phrase "based on" describes both "based only on" and "based at least on."

[0096] The term "processor" should be interpreted broadly to encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and so forth. Under some circumstances, a "processor" may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. The term "processor" may refer to a combination of processing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0097] The term "memory" should be interpreted broadly to encompass any electronic component capable of storing electronic information. The term memory may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with a processor if the processor can read information from and/or write information to the memory. Memory that is integral to a processor is in electronic communication with the processor.

[0098] The terms "instructions" and "code" should be interpreted broadly to include any type of computer-readable statement(s).For example, the terms "instructions" and "code" may refer to one or more programs, routines, sub-routines, functions, procedures, etc. "Instructions" and "code" may comprise a single computer-readable statement or many computer-readable statements.

[0099] The functions described herein may be implemented in software or firmware being executed by hardware. The functions may be stored as one or more instructions on a computer-readable medium. The terms "computer-readable medium" or "computer- program product" refers to any tangible storage medium that can be accessed by a computer or a processor. By way of example, and not limitation, a computer-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. It should be noted that a computer-readable medium may be tangible and non-transitory. The term "computer-program product" refers to a computing device or processor in combination with code or instructions (e.g., a "program") that may be executed, processed or computed by the computing device or processor. As used herein, the term "code" may refer to software, instructions, code or data that is/are executable by a computing device or processor.

[00100] Software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of transmission medium.

[00101] The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

[00102] Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein, such as those illustrated by Figures 9-11, can be downloaded and/or otherwise obtained by a device. For example, a device may be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via a storage means (e.g., random access memory (RAM), read only memory (ROM), a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a device may obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. For example, some of the methods described herein may be performed by a processor 1303 and or more local oscillators (LOs), a wideband receiver 119 and fast Fourier transform (FFT) hardware 121, software and/or firmware.

[00103] It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.

[00104] What is claimed is:

Claims

1. A method for wireless communication, comprising:

beginning acquisition;

performing an acquisition scan of ARFCNs for supported bands in an adjustable scan list;

identifying a home PLMN from a SIM card;

identifying a possible list of PLMNs expected in the region;

determining whether all expected PLMNs in the list of PLMNs expected in the region were found during the acquisition scan; and

determining whether the home PLMN was found during the acquisition scan.

2. The method of claim 1, wherein all the expected PLMNs were found during the acquisition scan.

3. The method of claim 2, further comprising decreasing the number of ARFCNs in the adjustable scan list.

4. The method of claim 1, wherein the home PLMN was found during the acquisition scan.

5. The method of claim 4, further comprising decreasing the number of ARFCNs in the adjustable scan list.

6. The method of claim 1, wherein the home PLMN was not found during the acquisition scan, and further comprising extending the acquisition scan to scan additional ARFCNs.

7. A method for wireless communication, comprising:

maintaining a PLMN database;

identifying known PLMNs from the PLMN database that should be available for a current area/region;

performing an acquisition scan of ARFCNs for supported bands in an adjustable scan list; and determining whether all the known PLMNs have been found.

8. The method of claim 7, wherein all the known PLMNs have been found.

9. The method of claim 7, wherein all the known PLMNs have not been found, and further comprising continuing to perform the acquisition scan.

10. The method of claim 9, wherein all the known PLMNs have not been found and every cell in the adjustable scan list has been scanned, and further comprising updating the PLMN database.

11. The method of claim 10, wherein updating the PLMN database comprises: performing a full search of all available ARFCNs;

adding newly found PLMNs to the PLMN database; and

removing PLMNs from the PLMN database that have not been found for a number of full scans.