Abstract: A method for determining a mobile communication terminal user's points of interest, in which geographic information of an area where the mobile communication terminal user stays longer than a threshold time, and an apparatus for providing the geographic information using the method. The method includes providing identification information received from a mobile communication repeaters, which use a limited number of the identification information and repeatedly reuse the identification information at different places.

Abstract: Whether relative velocity between a transmitter and a receiver is higher than a predetermined amount is detected. This involves using a Doppler estimation technique to generate an estimate of Doppler spread, {circumflex over (f)}D(1), based on a received signal, and using an alternative velocity estimation technique to generate an estimate of velocity, {circumflex over (v)}, based on the received signal, wherein the alternative velocity estimation technique differs from the Doppler estimation technique. A plurality of estimates, including at least the estimate of Doppler spread and the estimate of velocity, are used to detect whether the relative velocity between the transmitter and the receiver is higher than the predetermined amount. The alternative velocity estimation technique may, for example, be a second Doppler estimation technique that differs from the other Doppler estimation technique.

Abstract: Fast transitions between access points (APs) in a wireless network may be accomplished when a mobile unit (MU) moves between the APs, by causing a first tunnel to be established between the APs, and causing a second tunnel to be established between the new AP and the MU. A data path having established security and quality of service parameters between the MU and the old AP may be extended through the tunnels, so that communication with the MU is not disrupted while transitioning between APs. Transition processing thus may be decoupled from movement of the MU, so that the MU may continue to receive access to data over the data path. Optionally, once the data path has been so extended, the MU and new AP may engage in authentication and other messaging to formally affect a handover of the data path to the new AP. The APs and MU may be configured to communicate according to the 802.11 protocol.

Abstract: A system and method for cell reselection in a radio communication network is provided. The system comprises a mobile terminal transmitting a receive signal strength list after measuring signal strengths of at least a neighbor cell; and a host system selecting a cell suitable for the mobile terminal based on a suitable cell list and the receive signal strength list and transmitting the cell reselection information to the mobile terminal. The suitable cell list comprises information representing whether or not the neighbor cell is suitable for selection by the mobile terminal.

Abstract: A method and apparatus for wireless communication in which groups of expected mobile device mobility speed ranges are established. A first sub-carrier block arrangement for the group having the lowest expected mobility speed range is determined. The first sub-carrier block arrangement is comprised of a plurality of sub-carriers. A second sub-carrier block arrangement for a group having an expected mobility speed range faster than the expected speed range of the lowest expected speed range group is determined. The second sub-carrier block arrangement is comprised of the plurality of sub-carriers. The first and second sub-carrier block arrangements are different but use the same sub-carrier spacing and symbol duration.

Abstract: A dual mode mobile terminal has a dual mode in which said mobile terminal can be connected to any of two different wireless communications systems (hereinafter referred to as systems 1 and 2). The mobile terminal can be connected to optimum wireless communications system by considering conditions at which the mobile terminal is (moving speed, communication data rate) even if it is in the state of communicating using any of systems 1 and 2. The mobile terminal (3) which can be connected to any of the system 1 having a wide service area and medium and low communication data rate and the system 2 having a local service area and high communication data rate determines whether or not it is in the service area of the systems 1 and 2.

Abstract: The present invention relates to supporting media independent handover of a mobile terminal to a heterogeneous network. Preferably, the present invention establishes a unified interface to an upper layer of the mobile terminal for managing messages to and from at least one of a homogeneous network and a heterogeneous network. Furthermore, the present invention requests a scan of a heterogeneous network different from a current network of the mobile terminal via the unified interface to determine the presence of an accessible link of the heterogeneous network for performing the handover.

Abstract: A method for operating a mobile equipment (ME 10) in a wireless network (12) includes receiving from a wireless network a parameter that is indicative of a signal quality experienced by the ME, such as by determining a speed of the ME; calculating in the ME an indication of link quality, the calculation employing a filtering operation having a filter length that is a function of the determined parameter, such as speed or derivative of the speed of the ME; and reporting the calculated indication of link quality to the wireless network. The wireless network derives an indication of ME speed and transmits the speed indication to the ME using a point-to-point message.

Abstract: A base transceiver station used in a wireless communication system in which the location of each base transceiver station antenna is included in a coverage area of another base transceiver station antenna, the base transceiver station including a measuring unit measuring a distance between a mobile station and a base transceiver station antenna to which the mobile station is communicatively connected. The base transceiver station includes a switching unit switching the communication connection of the mobile station to another base transceiver station antenna when the distance measured by the measuring unit becomes less than or equal to a predetermined value.

Abstract: A hierarchical assignment manager (HAM) improves system throughput in a hierarchical overlay network by taking into account the requested data rates in addition to or instead of the velocities of mobile users within the network. The user population is characterized by the statistical description of their user profiles. The entire set of profiles is partitioned along assignment curves into two or more subsets, where each subset corresponds to the assignment to a particular layer of a hierarchical network. The HAM determines assignment curves to optimize the total effective system throughput in a systematic way and can be adapted to time-varying user behavior and profiles. The HAM can be used to decide upon assignment strategies between different layers of an overlay architecture, between different available network technologies, or between competing service providers.

Abstract: Methods and systems are provided for implementing mobile-station and macro-network-aided location determination of a low-cost Internet base station (LCIB). In an embodiment, a location of a mobile station that is associated with an LCIB is determined. The location of the mobile station is used to determine a location of the LCIB.

Abstract: A mobile broadband wireless system including at least two pairs of nodes arranged in a cluster, each pair coupled to form a link for wireless communication. Each node includes an RF transceiver with associated modem, an antenna array arrangement coupled to the modem and arranged for multiple concurrent transmissions, where each antenna has a beam pattern selected to improve quality of transmission, and a controller for controlling the transceiver, modem and antenna array arrangement for providing point to point communication. The controller allocates MIMO streams and modulation to different antennas in the antenna array arrangement, and implements at least one interference mitigation mechanism to minimize interference within the cluster during multiple concurrent transmissions. A method of wireless communication is also provided.

Abstract: The present invention relates to a method, call handling server (18), local wireless network (10) and computer program product for performing vertical handover of a wireless voice connection, which is a part of a voice connection set up between a portable communication (22) device and another device. The network comprises a number of access points (20) and the call handling server (18) for controlling voice connections to the portable device. The server comprises a control unit (24) that determines a handover situation for the wireless connection to the portable device based on a set of handover factors that comprise the position and movement of the portable communication device in an area of the local network and structural layout information of the area together with knowledge of where in this area there is insufficient coverage.

Abstract: A deadlocked state in which each communication station cannot recognize mutual existence is evaded to form a self-organized distribution type multi-channel wireless network. In some interference situations, a beacon transmission channel selected on a self criterion is not always a receivable channel for all of neighbor communication stations. A communication station receiving interference from another system periodically transmits an interference annunciation signal (IAS) through all channels under no interference, and informs the neighbor stations of the existence and the channel under interference. Thereby, transmission of a beacon is restrained through the channel under interference up to a beacon-unhearable degree.

Abstract: A communication system transitions from a high velocity mode of operation to a non-high velocity mode of operation based on a movement of a mobile station. When the communication system is in a high velocity mode of operation, the communication system promotes pilots from a High Velocity Neighbor Set of the mobile station or a controller. When the communication system is in a non-high velocity mode of operation, the communication system promotes pilots from a Neighbor Set of the mobile station or the controller. The communication system may further include a high velocity repeater that, when co-located with the mobile station, is capable of providing a communication link between the mobile station and a radio access network servicing the mobile station.

Abstract: An access point (AP) (120a) manages and coordinates the switching of mobile devices (110) to other access points (120b, c, d). The access point (120a) monitors the quality of its communications link with the mobile device (110). When the access point (120a) determines that the quality is degrading, or when the access point (120a) determines that its traffic is excessive, or when another switch-triggering event (202) occurs, the access point (120a) sends a transfer-request to other access points (120b, c, d) in its vicinity. If another access point can accept the mobile device (110), it notifies the requesting access point (120a) that it is available. The requesting access point (120a) selects from among the available access points (120b, c, d), and notifies the mobile device (110) to switch to the selected access point.

Abstract: At least one embodiment of the invention provides an automated frequency offset compensation method, system, and apparatus that improves throughput between one or more wireless communication devices by compensating for frequency offsets caused by a Doppler effect. In particular, one implementation estimates the frequency offset and uses this to compensate the carrier signal power to interference power ratio (C/I) when the transmitting and receiving devices are moving relative to each other such that a Doppler effect creates a frequency offset in the perceived frequency of the received carrier signal.

Abstract: In a mobile communication system in which a compressed mode can be activated at the time of hand over, or when a base station which the mobile station is in communication with is switched to another base station, the distance between the mobile station and at least one of the plurality of base stations which is currently in communication with the mobile station is measured; and the activation of the compressed mode is controlled according to the measured distance. The activation of a compressed mode is controlled according to the distance between the base station and the mobile station.

Abstract: A system and method for accommodating a rapid transition between heterogeneous radio access technologies is provided. A local network 105 having a controller 114 and a plurality of access points 106,107,108,109,110,111 receives information 117 from a communication device 101 relating to the network 116 it is exiting. During the transition process from a first network 116, for example a cellular wide area network, to a second network 105, for example an IMS-WLAN, the communication device 101 passes its wide area network servicing base station information 117 to an access point 106 of the local network 105. Upon exiting the local network 105, wide area network servicing base station information 121 is delivered to an exiting communication device 112, thereby enabling it to abbreviate or eliminate traditional scanning and acquisition processes that occur in network handoff exchanges.

Abstract: A virtual network is created by providing antennas controlled by the same base station with control signals of different virtual base stations. A virtual network controller comprised in the base station is arranged for performing handovers between sets of physical channels of the different virtual base stations. The handover is preferably performed transparently towards the main communication network. This transparency is preferably provided by associating physical channels of virtual base stations with communication channels of the main communications network. Preferably, position estimations of a mobile terminal connected to the base station are performed by the virtual network controller, whereby such estimations can be kept secret within the virtual network.

Abstract: A system, computer readable medium, mobile subscriber device and method determine that the device (306), operating on a first communications system is detecting a triggering event, which may be the detection of a wireless local area network border cell (210) or a degradation in signal quality. The device (306) then initiates a registration sequence with a second wireless communication system if the device (306) has detected the triggering event, determines the speed and/or displacement of the device (306), and conducts any present and subsequent calls via the second wireless communication system if the speed and/or displacement of the device exceeds a predetermined threshold. The registration sequence may be aborted if at least one of the speed and displacement of the device (306) does not exceed predetermined thresholds. Movement of the device (306) may be determined by an accelerometer (314) or GPS chipset.

Abstract: In a radio mobile communication system adopting a hierarchical cell structure comprising a plurality of layers having respective cells of different sizes, the threshold value of the number of times of cell reselections and/or the threshold value of the time required to measure the number of times of cell reselections are set for each layer. A mobile station device compares the number of times of cell reselections in a specific time and/or the time required for the number of times of cell reselections to reach a specific value with the threshold values and selects a transfer target cell.

Abstract: An apparatus and method for performing an interfrequency hard handoff at a border cell in a wireless network. The apparatus comprises a handoff controller within a source base station that selects an optimal target base station using location information of at least one target base station and using one of: a location of the wireless mobile station, a velocity of the wireless mobile station, and a direction of motion of the wireless mobile station. The present invention uses the location information of at least one target base station in order to make more reliable handoff decisions.

Abstract: A mobile switches operation for communications from a wireless wide area network (WWAN) to a wireless local area network (WLAN) in an efficient manner. While providing operation for communications in the WWAN, the mobile device continually maintains visited cell site history information which is indicative of visited cell sites of the WWAN that served the mobile device over a moving time period of its operation. The mobile device continually monitors this information to identify whether it has been contained within a local geographic region over the moving time period. When the mobile device is identified to have been contained within the local geographic region, it is permitted to operate for communications with the WLAN, and may enable its WLAN radio transceiver and select the WLAN for communications.

Abstract: The embodiment of the invention is related to a processor configured for determining a predetermined number of frequency estimates, determining an average of the frequency estimates for obtaining an averaged frequency offset, unbiasing received samples and/or impulse response values using the averaged frequency offset, calculating Doppler frequency estimates using the unbiased received samples and/or impulse response values and calculating selected second order statistics of the Doppler frequency estimates over a predetermined period and calculating a speed of a communication system terminal using the Doppler frequency.

Abstract: A system is provided for selecting a cell to which to hand off a user equipment (UE). The system includes a processor programmed to promote evaluation of a plurality of mobility drivers for one or more neighbor cells of a cell serving the UE (user equipment). The processor programmed to promote evaluation of a plurality of groups of mobility drivers based on the evaluations of the mobility drivers, wherein the UE is handed off to one of the cells based on the groups of mobility drivers that are evaluated positively.

Abstract: An apparatus and method of effecting hand-off of a mobile station in a first wireless communication system, which has a first mobile switching node operable with a first base station and a second mobile switching node operable with a second base station, and a second wireless communication system, is claimed. A handoff required message is received at the first mobile switching node, and sent to a second mobile switching node. A message from the second mobile switching node is sent to request allocation for a handoff. In an embodiment, this message is sent to the VLR of the second wireless communication system. In response, a handoff request acknowledge message is received by the second mobile switching node and sent to the first mobile switching node. An initial address message is sent to initiate a circuit connection between the first mobile switching node and the second mobile switching node. Then, the call is received from the first mobile switching node.

Abstract: A method in a communication system comprising a access network with Radio Network controllers (RNC) and radio base stations (RBS or Node B) consisting of main units (MU) which performs base band signal processing and one or more radio remote units (RRUs) which converts between baseband and radio frequencies and transmits and receives signals over one or more antennas, covering cells, and one or several User equipment (UE or Phones) moving closer and closer to another cell, which said network is made aware of and then it will initiate a handover process, during which the call will be transferred from one cell to another cell within said radio base station (RBS or Node B)or to a cell in another Radio base station (RBS or Node B)in said communication network. Said handover process interact with a memory containing a list (softer handover group) of said radio remote units (RRUs) capable of doing softer handover with each other using the same Rake receiver.

Abstract: A system and method for management of communication links between nodes in a wireless communication network (100). The system and method perform the operations of estimating an expected rate of change in the characteristics pertaining to communication over a communication link in the network (100), and assigning a value associated with the link based on the expected rate of change. The system and method also adjust the rate of change of the value associated with the link based on the condition of the link.

Abstract: A method and apparatus are provided for enabling a UE to perform accurate and efficient cell reselection in a cellular mobile communications system. If reselection to the same cell is repeated, the UE releases itself from a high-speed UE state or excludes the number of reselections to the same cell from the number of cell changes counted for a duration set for deciding as to the high-speed UE state, according to a ping-pong duration threshold and a ping-pong occurrence number threshold. The UE uses a non-scaled down cell reselection time limit in a non-high-speed UE state, and a scaled-down cell reselection time limit in the high-speed UE state. Thus, the UE reselects to a non-serving cell having the highest ranking continuously for the cell reselection time limit.

Abstract: Apparatus and methods are provided for adaptively determining a handover measurement interval. Power savings are achieved when a mobile terminal in a digital broadcast broadband network does not constantly attempt to measure the signal strength of nearby cells. By determining cell parameters, such as size and carrier frequency, and also determining dynamic information, such as signal strength and mobile speed over time, the time until the next handover measurement is adjusted up or down. When a mobile terminal is moving towards a transmitter in a cell, the handover measurement interval may be lengthened, and when a mobile terminal is moving away from a transmitter, the interval may be shortened.

Abstract: A method and apparatus are provided for adapting a pilot filter based on the velocity of a wireless communication device (WCD) in relation to a wireless network infrastructure. The pilot filter is adapted by determining pilot coefficients for the pilot filter based on the WCD velocity. The pilot filter may be located in the WCD, or in the network infrastructure, or in both.

Abstract: A system and method for allocating a search resource of a base station modem is provided. The system comprises search controlling units for receiving an allocated search resource and searching a multi-path of a radio channel to produce a search result; measuring units for measuring mobility of a terminal based on the search result; and allocating units for adaptively allocating a common search resource to the search controlling units based on a measure of mobility of the terminal.

Abstract: A system for geographically locating and tracking mobile stations within a mobile communication network. The system includes an equipment identity register (EIR) comprising equipment identifiers, such as internal mobile equipment identities (IMEIs), subscriber identity modules (SIMs), or some combination thereof, that are each uniquely associated with mobile stations operable within the network. Each IMEI may be used to identify a particular status of an associated mobile station. A mobile switching center (MSC) or an external location services (LCS) client may be configured to identify a targeted mobile station based upon its status (for example, lost, stolen, malfunctioning, and the like). A serving mobile location center (SMLC) responsively provides position location information for the targeted mobile station.

Abstract: Mobile devices (121, 122, . . . , 12n) are handed off in overlapping cells (181, 182, . . . , 18n) by tracking a velocity (speed and direction) of movement of any number of the mobile devices (121, 122, . . . , 12n). Access points (141, 142, . . . , 14n) are each located in an associated operational cell (181, 182, . . . , 18n) and each operates at a dedicated frequency. The initial signal strengths are measured in advance at predefined locations within a defined space (16) to define signal strengths as location map (42). A nearby initial access point (typically the nearest) and at least two nearby (typically next nearest) access points are assigned for one of the mobile devices (121, 122, . . . , 12n), and the frequencies of each access point identified. A tracking processor (50) periodically scans the frequencies of the nearby access points to determine the location velocity of the mobile device and predict when a handoff will be appropriate. E.g.

Abstract: A hierarchical cell structure that may be applicable to any wireless communications network utilizing cells. One or more characteristics associated with a mobile device configured to communicate with the base stations via a wireless communications protocol are determined while the mobile device is communicating with a base station. The one or more characteristics are utilized to determine a subsequent base station to be the target of a handoff procedure.

Abstract: Methods and apparatus are disclosed for implementing a speed sensitive mobile network device (e.g., Mobile Router). The speed of the mobile network device is detected. The values of one or more operating characteristics of one or more interfaces of the mobile network device are ascertained, where the values correspond to the speed of the mobile network device. One of the interfaces having a desired set of values of the operating characteristics at the speed of the mobile network device is then selected.

Abstract: A method of mobile terminal for handover/switch among different wireless communication networks in a heterogeneous network environment is provided. The presented method can optimize battery life by switching off the radio functionality or signal detector when it is not required, based on the movement information, ex. velocity, of the mobile terminal in the heterogeneous wireless communication network. This method will determine an optimal time to turn off the signal detector for minimizing the power consumption. Furthermore, when the mobile terminal moves continuously but the coverage of the preferred wireless network is relatively small, this method can also avoid redundant and unnecessary handover for keeping the communication quality stable, and reduce the loading of frequent handover in the heterogeneous network.

Abstract: A communication unit (CU) (109, 111) network controller (113) and corresponding methods (603-609) are described that facilitate selectively routing calls. The CU includes a transceiver (403) suitable to support an air interface with a local area network (LAN) (101) and with a wide area network (WAN) (105) and a controller (405) that is coupled to and controlling the transceiver. These are each and collectively configured to determine when a bearer leg within the WLAN will not support a call attempt over the bearer leg and responsive to so determining, initiate the call over another bearer leg, e.g. within the LAN or the WAN. The determining includes, for example, receiving a message (703, 707, 713) that indicates or implies that the call can not be supported.

Abstract: Speed indication device (100) for determining a speed indication signal (410) indicating a speed of a wireless mobile telecommunication device (14) relative to the speed indication device (100), wherein the speed indication device (100) determines the speed indication signal (410) from a sequence of transmit power control commands sent by the wireless mobile telecommunication device (14) to an access point (12) in a wireless telecommunication device (14) to an access point (12) in a wireless telecommunication network for controlling, in use, a transmit power of a radio signal transmitted by the access point (12) to the wireless mobile telecommunication device (14). If the relative speed is found to be above a threshold, the speed may be calculated using a measurement of the Doppler frequency.

Abstract: A communication system comprises a downlink data channel for the transmission of data packets from a primary station to a secondary station and uplink and downlink control channels. The secondary station measures one or more characteristics of the data channel and issues a report to the primary station, which determines an operational parameter of the data channel in response to the report. The secondary station determines average channel characteristics over a measurement period. The length of the measurement period may be signalled by the primary station or determined directly by the secondary station. In one embodiment the selected period depends on the speed (V) of the secondary station. This is determined (604) by either station and tested to determine (606) whether it is outside the range for the current measurement period: if it is the period is reset (608).

Abstract: A UE performs pilot measurements over a frequency sub-band of serving cell and adjacent cells based on pilot symbols for used in handover. UE uses channel quality measurement result to adjust frequency sub-band and periodicity of pilot measurement. In interference coordination scheme, UE is classified into cell edge or cell center UE based on channel quality measurement result. For downlink data reception, UE in cell edge is allocated cell edge frequency sub-band and UE in cell center is allocated with cell center frequency sub-band. If UE is in cell edge of the serving cell, UE also performs pilot measurement over cell edge frequency sub-band. If UE is in cell center, UE also performs pilot measurement over cell center frequency sub-band of the serving cell. When UE is located in cell edge, it performs measurement at a higher rate than when it is located in cell center.

Abstract: A method for operating a mobile equipment (ME 10) in a wireless network (12) includes determining a parameter that is indicative of a signal quality experienced by the ME, such as by determining a speed of the ME; calculating in the ME an indication of link quality, the calculation employing a filtering operation having a filter length that is a function of the determined parameter, such as speed or derivative of the speed of the ME; and reporting the calculated indication of link quality to the wireless network. The step of determining includes steps of (a) deriving an indication of ME speed in the wireless network; and (b) transmitting the speed indication to the ME using a point-to-point message.

Abstract: An apparatus and method is disclosed for selecting a handoff target base station in a wireless network. The apparatus comprises a handoff controller within a wireless mobile station that selects an optimal target base station for handoff based on pilot signal strength measurements of at least two candidate base stations and one of: a location of the wireless mobile station, a velocity of the wireless mobile station, and a direction of motion of the wireless mobile station. The present invention uses more than just pilot strength measurements to select an optimal target base station for handoff. Incorporating position location information in the handoff decision causes the handoff decision to be more reliable. This reduces the number of unnecessary handoffs and results in better system performance.

Abstract: A base station apparatus and method for estimating a velocity of a mobile station in a mobile communication system are provided. In the apparatus and 9 method, a channel estimator receives a signal on a radio channel from the mobile station and performs channel estimation using the received signal. A velocity estimator detects a power spectrum value of the channel estimator, and provides the channel estimator with a channel estimation coefficient for use during channel estimation according to a Doppler shift frequency value of power estimated from the mobile station when the velocity of the mobile station is unchanged.

Abstract: A mobile station and a method are provided for determining to perform a handover based on information of movement between cells. Signals transmitted from a serving base station and a neighboring station may be scanned at a periodic interval, the power of the transmitted signals may be measured, and the power of the transmitted signals from the serving base station is compared to a critical power. A movement discriminator denoting whether the mobile station lies in a cell of the serving station may be formed based on the power of the transmitted signals when the signal power of the serving base station is less than the critical power. The movement discriminator may be stored accumulatively, and performance of handover may be decided based on the discriminators stored accumulatively.

Abstract: A method for reducing a delay in a wireless communications system resulting from a handoff while mitigating a risk of premature termination of wireless communications, the method includes comparing data indicative of actual use of the wireless communications systems to at least one predetermined criteria. If the comparing determines a sector pairing in the wireless communications system to be statistically significant for purposes of recommending at least one search window setting, at least one value related with a distance associated with the sector pairing may be used to automatically determine a corresponding signal delay. If the corresponding signal delay exceeds a prior determined signal delay, a recommended search window setting may be determined using the corresponding signal delay.

Abstract: System and method for the adaptive control of VHF communications in aircraft. In one embodiment, the invention includes an adaptive communications system for an aircraft having a communications processor that accesses a communications switching model to select a preferred ground communications station. In another embodiment, a method of communication between an aircraft and a ground station includes receiving a communications switching model and determining a flight parameter for the aircraft as the aircraft navigates along a flight route and selecting a ground station based upon the determined flight parameter. The aircraft then communicates with the selected ground station. In still another embodiment, a method for compiling a communications switching model includes receiving signals from a ground station and measuring a signal strength. A preferred ground station is selected based upon the measured signal strength value.

Abstract: A method is provided of determining the movement context of a mobile user terminal in a wireless telecommunications network by the steps of: determining a time at which transfer to a first cell occurs, determining a time at which transfer from said first cell first subsequently occurs, determining the difference between the two times, and assigning a movement context to the mobile user terminal, said context being dependent upon said difference.

Abstract: A mobile communication system using an orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) scheme. The method for assigning ranging codes in the OFDM/OFDMA communication system includes classifying rangings between a base station and a mobile subscriber station (MSS) of the OFDM/OFDMA communication system into an initial ranging, a periodic ranging, a bandwidth request ranging, and a handover ranging. A first number of ranging codes used for the rangings are created and a second number of ranging codes selected from the first number of ranging codes are assigned as handover ranging codes used for the handover ranging.