Abstract: A wireless communication system using channel access based on a contention approach and method thereof is disclosed, which allocates plural sets of time slots in a predetermined contention interval, wherein each set of time slots further includes plural adjacent overlapped time slots. A channel requester transmits a contention message to a channel allocator at a time slot based on an interleaved method after the channel requester completes count down of a predetermined time, so that the positions of the headers of the contention messages in the adjacent time slots of each set of time slot are different. Thus, if the contention message transmitted by the channel requester collides with the contention message of the adjacent time slot, the channel allocator can parse the headers of the collided contention messages and respectively allocate plural special channel times for communicating with the channel requesters.

Abstract: The present invention provides a system and method that operates in the link layer and detects connection status in a LAN. The system includes a request frame whose source address is an address of a node transmitting the request frame, a reply frame whose destination address is the source address of the request frame, and a first node and a second node within the LAN for processing the request/reply frame. The method includes the first node transmitting a request frame into the LAN, the second node transmitting a reply frame to the first node if receiving the request frame, and the first node checking whether a destination address of the reply frame comprises an address of the first node when receiving the reply frame. If so, the connection between the first and second nodes is in a normal state.

Abstract: A method for operating in a network that includes one or more of the following: assigning a respective active member address to each of a plurality of first slave nodes participating in a piconet; receiving a request to join the piconet; determining that no more different active member address are available in the piconet; determining that a second slave node supports extended addressing; and performing calculations as a function of the bandwidth requirements of the second slave node to determine whether to share an assigned active member address with the second slave node.

Abstract: A method and system for increasing the efficiency of providing bandwidth for voice traffic to a data provider via wireless communication mediums is provided. This is generally accomplished by not transmitting any data during the silence periods and playing out background noise (i.e., comfort noise) at the other end, to obtain significant bandwidth savings.

Abstract: In a wireless local area network, an access point failing to adhere to proper power management protocol is detected by analyzing a beacon frame sent by the access point to determine if a traffic information map (TIM) in the beacon frame is zero. A frame sent by a station is analyzed to determine if the station is in a power save mode. A data frame sent by the access point is analyzed to determine if the data frame is destined for the station. An improper power management protocol condition of the access point is determined based on the foregoing analysis.

Abstract: A method and system for increasing the efficiency of providing bandwidth for voice traffic to a data provider via wireless communication mediums is provided. This is generally accomplished by not transmitting any data during the silence periods and playing out background noise (i.e., comfort noise) at the other end, to obtain significant bandwidth savings.

Abstract: A data transmission method in a wireless LAN, an access point device and a station device are provided. The data transmission method for transmitting data from an access point on a wireless LAN includes allocating a sub-contention free period in which 802.11 based legacy stations and high throughput (HT) stations with multiple antennas obtain a channel use right through polling, and an HT contention period in which the HT stations can obtain a channel use right through contention. According to the method and devices, when there are no objects of polling in a contention free period, the period, in which the HT stations can obtain the channel use right though contention, is made to begin earlier such that without wasting the channel use period, the channel can be used flexibly.

Abstract: A modem that provides efficient use of wireless network bandwidth in the presence of multi-user interference and noise comprising a multi-user detection module (115), a data formatting module (120), a control processor (125) and a demultiplexer (135).

Abstract: An access point is to handle received broadcast or multicast traffic as multiple instances of unicast traffic, where each instance is destined for a corresponding wireless client device associated with the access point. A client device may adjust its listen interval parameter according to predefined considerations, for example a charge level of a battery to power the client device and an expected usage model for the device. A client device may initiate a reassociation request to inform the access point of its adjusted listen interval parameter.

Abstract: A limited acknowledgement-based communication methodology increases the throughput efficiency of extended range, wireless packetized data transmissions to a ‘master’ data-reception site from a ‘slave’ data-sourcing site, geographically remote with respect to the data-reception site. Rather than return an acknowledgement for each received packet, the master returns an acknowledgement only after receipt of a group of packets. When returning an acknowledgement, the master identifies which packets of the group were not successfully received. Missing packets may be retransmitted by the slave transmitter either immediately, or in response to a subsequent poll by the master.

Abstract: Backward compatibility may require the use of fields or other indicators that are interpreted by new nodes or stations in a system in a manner different from the way legacy nodes interpret those same fields. In some circumstances, these indicators may be used to “spoof” legacy nodes to behave in certain ways, to allow a next generation protocol to be performed without interference from those legacy nodes. While this practice is may increase communication effectiveness, spoofing may lead to inefficient operation of legacy nodes. Legacy nodes may detect spoofing, including detecting field settings in a legacy portion of a transmitted message, or detecting phase shifts in a message. Once spoofing is detected, a variety of steps may be taken, including determining the duration of the next generation message, entering a low power state for the duration, communicating on alternate channels for the duration, modifying legacy backoff procedures, and others.

Abstract: A method for accessing a wireless local area network (WLAN) channel and providing quality of service (QoS) for voice in a system supporting both voice and data services. Under the method, a communication device (302, 303) contends for a medium (channel). Upon identifying a transmit opportunity, the device transmits a voice packet to an access point (AP) (304) and polls the AP for downlink traffic. A low power implementation is feasible because the communication device can sleep, wake up to contend for the medium, transmit a voice packet to the AP, request a voice packet from the AP, transmit an acknowledgement, and go back to sleep.

Abstract: A method (500) is provided for dynamic packet polling during a power save mode. The method can include polling (504) an access point (104) for packets at a first rate on at least one access category, determining (506) a polling time-out as a function of a packet priority, and possibly changing the rate to a second rate in view of a second packet priority. The polling time-out can correspond to a duration interval of the polling for increasing an efficiency of the power save mode. The method can include establishing a poll timeout and an overall poll timeout as a function of each access category. The function can include mapping a packet priority to a response time for setting a timeout. In one aspect, the polling can be combined into a single polling stream for multiple access categories.

Abstract: An apparatus and method for channel estimation and CP reconstruction in an OFDM-STBC mobile communication system are provided. An ISI canceller cancels ISI signal components from first and second received symbol sequences. A cyclicity restorer cancels ICI signal components from the ISI-cancelled first received symbol sequence and the ISI-cancelled second received symbol sequence. A recoverer acquires the recovered sequence estimates of the ICI-cancelled first received symbol sequence and the ICI-cancelled second received symbol sequence by decoding. The ICI cancellation of the ISI-cancelled first and second received symbol sequences and the ISI cancellation of the second received symbol sequence are iterated a predetermined number of times.

Abstract: A method and apparatus of scheduling jobs each having respective (i) length of execution time and (ii) requested frequency of occurrence includes for each given job, allocation of a respective set of start times in a cycle in a manner that evenly spreads the given jobs over the cycle. Idle time slots are added or padded into the cycle in a manner which reduces jitter (i.e., the differences in spacing between consecutive occurrences of the same job). The method and apparatus enable a balance between period approximation and jitter reduction to be optimally achieved.

Abstract: A method for interoperability of a network interface protocol with an Internet interface protocol begins by receiving a scan channel request of a plurality of channels that are in accordance with the network interface protocol. The method then continues by determining whether an Internet packet is being received via one of the plurality of channels when the channel scan request is received (i.e., is a higher layer protocol supporting a current transmission). If so, the method continues by scanning at least one channel of the plurality of channels, but does not scan all of the plurality of channels at one time. The method continues after the scanning by tuning to the channel supporting the higher layer protocol communication to transmit at least one outbound Internet packet. The method then continues by scanning at least another channel of the plurality of channels.

Abstract: A method of operating a Base Station (BS) in a broadband wireless communication system to resume an extended real-time Polling Service (ertPS) is provided. The method of operating the BS includes detecting a codeword received through a Channel Quality Indicator (CQI) channel, and upon receiving a CQI CHannel (CQICH) codeword for requesting resumption of an extended real-time Polling Service (ertPS) connection from a Mobile Station (MS), allocating to the MS an uplink resource corresponding to the largest maximum sustainable traffic rate of at least one ertPS connection established to the MS.

Abstract: Wireless internet in the in-vehicle environment is an evolving reality that reflects the gradual convergence of wireless and internet technologies. The present invention provides an application layer system that makes wireless internet access adaptive to dynamically changing heterogeneous network environments, by stressing carrier-independence and access transparency. To achieve these objectives, the present invention provides the following features: HTTP session continuity and automatic HTTP failure recovery; network environment awareness and application-level preemptive handoff based on bandwidth capacity.

Abstract: A method for communicating data in a wireless control area network, where the wireless control area network includes one or more sensor nodes configured to facilitate acquisition of patient data and an access coordinator configured to facilitate acquisition of the patient data from the one or more sensor nodes, is presented. The method includes creating a correlation between one or more poll packets from an access coordinator and time of arrival of data at one or more sensor nodes. Systems and computer-readable medium that afford functionality of the type defined by this method is also contemplated in conjunction with the present technique.

Abstract: A Bluetooth master radio frequency unit addresses a slave radio frequency unit, to enable the slave to resynchronize to the master, by sending poll packets or null packets, the master being arranged to send sufficient null packets to enable the slave to resynchronize, before sending a poll packet, to determine whether the slave has resynchronized. This approach can provide the slave with the same number of synchronization packets as in the simpler algorithms, while allowing the slave to preserve more (transmit) power and still allowing the master to detect whether the slave has resynchronized or not (and thus to update a Link Supervision Timer for example). Notably this is also suitable for use in prescheduling implementations.

Abstract: An embodiment of a method for link management in a scatternet, performed by a wireless communication device, is provided. The wireless communication device simultaneously establishes a synchronization link in a first piconet, and an asynchronization link in a second piconet. The embodiment of the method contains the following steps. At least one time interval originally utilized for packet transmissions in the synchronization link is sacrificed. During the sacrificed time interval, the asynchronization link is switched to for a time period to maintain connection between the wireless communication device and a peer device operating with the asynchronization link.

Abstract: A link restoration mechanism includes sending status-inquiry messages at a varying rate between two devices. Under normal operating conditions, keep-alive messages are sent from one device to another to determine the status of the communication link. The keep-alive messages are sent periodically to achieve an on-going status of the communication link between the two devices. If a pre-determined percentage of keep-alive messages fail to be received or are invalid, the communication link is declared down, that is, not functioning correctly, and data exchanges between the two devices cease. Whenever the communication link is suspected to be down due to a disruption in the sending of keep-alive messages, keep-alive messages are sent at an accelerated rate. Thus, after a pre-determined number of valid responses are received the communication link can be declared functioning normally and data exchanges between the two devices can continue.

Abstract: A method of polling in a wireless communications system includes prohibiting polling within a predetermined period and triggering a poll function while polling is prohibited. After the predetermined period has expired the method determines that there are no protocol data units (PDUs) scheduled for transmission or re-transmission and that there is at least a transmitted PDU that the poll function was triggered by a “Last PDU in buffer for first-time transmission” trigger, and selects a PDU to schedule for re-transmission to fulfill the poll function.

Abstract: To conserve energy, components in mobile devices have to transition less frequently between “active” and “sleep” modes, and to sleep for longer intervals. In accordance with at least one preferred embodiment of the present invention, there is broadly contemplated herein an approach for remote discovery of wireless client and access point configurations, especially those settings associated with the power consumption of the client's wireless interface. Methods contemplated in the preferred embodiment use packet probing techniques to determine the client and access point configurations remotely. The probing techniques include sending packets to the client device, over the wireless LAN, at intervals calculated using data publicly available on the wireless LAN technology in use and results of previous packet probing measurements. Measurements from several packet probes and methods for statistical data processing are used to make a determination.

Abstract: A method and apparatus for transmitting control information relating to an uplink packet data service from a user equipment (UE) to a Node B in a mobile communication system are provided. MAC-es protocol data units (PDUS) including data of an upper layer and a control service data unit (SDU) including control information of a MAC layer are multiplexed and contained in a MAC-e protocol data unit (PDU) transmitted in an uplink from the UE during one transmission period. In a header of the MAC-e PDU, a header part corresponding the control SDU contains a data description indicator (DDI) field set as a specific value representing that the control information is transmitted, and a header part corresponding to the MAC-es PDU contains a DDI field which represents a MAC-e flow and a logical channel relating to uplink packet data included in the second PDU, and a data size. Node B detects the control information from the control SDU based on the DDI field set as the specific value.

Abstract: A data session with a wireless device ordinarily cannot be initiated from the network side because the wireless device has no predetermined IP or other network address. Methods are disclosed for instead causing the wireless unit to initiate a data session with a target destination, thereby obviating the IP addressing problem. A voice call is first initiated by a requester application to a remote wireless unit. The requester transmits a request message to the remote wireless unit via the wireless voice channel using in-band techniques; preferably including a payload in the polling message that identifies the target destination. In response, the remote wireless unit initiates a packet data session with the target destination.

Abstract: A method and apparatus for a self-correcting bandwidth request/grant protocol in a broadband wireless communication system is disclosed. The self-correcting bandwidth request/grant protocol utilizes a combination of incremental and aggregate bandwidth requests. In accordance with the present inventive protocol, CPEs primarily transmit incremental bandwidth requests to their associated base stations, followed by periodic transmissions of aggregate bandwidth requests. The use of incremental bandwidth requests reduces risks that a base station erroneously issues duplicate bandwidth allocations to the same CPE for the same connection. Race conditions that may have occurred using only aggregate bandwidth requests are eliminated by requiring the CPEs to request bandwidth in an incremental manner. However, use of periodic aggregate bandwidth requests (that express the current state of their respective connection queues) allows the present bandwidth allocation method and apparatus to be “self-correcting.

Abstract: A limited acknowledgement-based communication methodology increases the throughput efficiency of extended range, wireless packetized data transmissions to a ‘master’ data-reception site from a ‘slave’ data-sourcing site, geographically remote with respect to the data-reception site. Rather than return an acknowledgement for each received packet, the master returns an acknowledgement only after receipt of a group of packets. When returning an acknowledgement, the master identifies which packets of the group were not successfully received. Missing packets may be retransmitted by the slave transmitter either immediately, or in response to a subsequent poll by the master.

Abstract: A method for handling a Timer_Status_Periodic timer in a wireless communication system includes starting the Timer_Status_Periodic timer for a Radio Link Control Acknowledged Mode (RLC AM) entity, performing a reset procedure for the RLC AM entity, and not stopping the Timer_Status_Periodic timer in response to the reset procedure.

Abstract: Systems and methods for implementing an enhanced multi-channel direct link protocol between wireless stations in a wireless LAN environment are disclosed. An exemplary method is implemented in a first wireless station that is part of an infrastructure basic service set network. The infrastructure basic service set network also includes an access point and a second wireless station. The wireless stations of the infrastructure basic service set network communicate on an infrastructure frequency channel. The method involves determining that at least one condition is satisfied for establishing a direct link with the second wireless station for transmission of data from the first wireless station to the second wireless station. The direct link is established with the second wireless station on a direct link frequency channel that is different than the infrastructure frequency channel. The data is transmitted to the second wireless station via the direct link.

Abstract: A method for maintaining the quality of transmission from a head end to a service unit in a telecommunications system that uses a multi-carrier transmission scheme with dynamic bandwidth allocation is disclosed. The method involves allocating a first payload channel to a service unit in a subband of a transmission channel of the telecommunications system and monitoring the quality of the first payload channel. When the quality of the first payload channel drops below a threshold, the method allocates a second, different payload channel to the channel unit.

Abstract: A system and method for remotely controlling an increased number of subsystems having an onboard locomotive control unit (LCU) and two associated operator control units (OCUs) on a single wireless channel. A time slot is assigned to each subsystem for making two-way transmissions to control the locomotive. A signal from an external timing source synchronizes each subsystem to minimize interference between transmissions from different subsystems. Time slots are assigned manually or automatically over a wireless network or by the LCU after monitoring the channel. The LCU automatically selects the direct or repeater transmission path depending upon whether or not it receives polling message responses from its associated OCUs. A GPS receiver in each subsystem receives the synchronization signal and provides geographic positioning data so the LCU can determine when to execute predefined, position-based commands. The secondary OCU may be turned off and rejoined to the subsystem without ceasing operation.

Abstract: A wireless communication system capable of saving time for mutual data communication in a sniff mode. The wireless communication system has: a master apparatus for calculating a sniff parameter including a time of a sniff period capable of performing the communication by allowing a corresponding device to commonly have the time in the sniff mode, when a communication mode for a mutual data communication by a user is selected to be operated in the sniff mode; and a sniff slave apparatus for performing the mutual data communication with the master apparatus by commonly having a corresponding time calculated in accordance with the sniff parameter. At this time, the sniff parameter includes at least one among a cyclic information, an allocated time information of the sniff period, and a start time information in which the master apparatus communicates with the sniff slave apparatus operated in the sniff mode.

Abstract: A method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded.

Abstract: An embodiment of the present invention provides an apparatus, comprising a wireless station operable in a wireless local area network, the wireless station capable of automatic discovery of other stations in a basic service set (BSS) which are capable of supporting direct link setup (DLS).

Abstract: This invention relates to an information processing apparatus, an information processing method, a recording medium, and a program for transmitting an RTS frame at full power and data at low power. If it is ascertained that data is to be transmitted, an RTS frame is transmitted at full power. If a CTS frame enabling data transmission is not received, a determination is made as to whether a CTS frame is received with its RA field carrying the address of another terminal. If the latter CTS is found to have been received, a transmission-prohibited interval is set and counted based on a duration field in the CTS frame. If the CTS frame enabling data transmission is found to have been received, a reception level of the frame is measured and stored. Data is transmitted by a PDA at lower power. An ACK frame is received. This invention applies illustratively to PDAs.

Abstract: A method and apparatus includes: at least one AP (Access Point) arranged to set and transmit a bit of a beacon message corresponding to a station for exchanging traffic, to register the station on a PS-polling list upon an acknowledgment of the beacon message being received, to assign a predetermined time slot to the station, and to transmit the traffic during the time slot, when at least one piece of traffic is exchanged for wireless voice communication; and at least one station adapted to be awakened into an active mode to parse the received beacon message, to calculate the assigned time slot when a bit of the station is set, and to awaken into the active mode during the assigned time slot to exchange the traffic, when the beacon message has been received from the AP upon being in a doze mode.

Abstract: A wireless network avoids delays in receiving status reports by having transmitters make sure that any outstanding Hybrid Automatic Repeat-reQuest (HARQ) processes in progress are all finished before sending the polling request. Thus, the receiver can respond to any polling request of the transmitter immediately without delay. Since the transmitter already ensures all HARQ processes are done, the receiver's status report will accurately reflect the latest information. The transmitter may send a poll anytime regardless of the HARQ processes if the most up-to-date polling is determined to be not as important (e.g., when the transmitter is trying to advance its transmitter window, in which case the exact Status info is not critical). The receiver may then react immediate upon receiving the poll. Thereby, detecting the loss of any piece of data within a data burst is expedited.

Abstract: A wireless communication system controls wireless communications over a shared wireless link. The wireless communication system transfers first credits to a first wireless communication device at a first credit transmission rate. The wireless communication system transfers second credits to a second wireless communication device at a second credit transmission rate. The first credits indicate first time periods for the first wireless communication device to use the shared wireless link. The second credits indicate second time periods for the second wireless communication device to use the shared wireless link. The wireless communication system changes the first credit transmission rate and changes the second credit transmission rate. In some examples, the wireless communication system changes the first credit transmission rate and the second credit transmission rate in response to collisions on the shared wireless link.

Abstract: In a networked system having a protected central server network connected to one or more satellite servers, the central server includes master data, and each satellite system includes replicated data derived from the master data. A corruption of at least a portion of the replicated data in one of the satellite servers is determined. Responsive to determining the corruption, at least the corrupted portion of the replicated data is replaced in the satellite server with data derived from the master data of the central server.

Abstract: A method for determining a measurement time period for measuring a propagation environment in a wireless station set having a plurality of wireless stations, between which wireless communication is made using a channel selected from a plurality of channels different in frequency. The method includes the steps of: obtaining a measurement time period in another wireless station set having a plurality of wireless stations; and determining the measurement time period in the own wireless station set so as to have a time period that does not overlap the obtained measurement time period.

Abstract: A data session with a wireless device ordinarily cannot be initiated from the network side because the wireless device has no predetermined IP or other network address. Methods are disclosed for instead causing the wireless unit to initiate a data session with a target destination, thereby obviating the IP addressing problem. A voice call is first initiated by a requester application to a remote wireless unit. The requester transmits a request message to the remote wireless unit via the wireless voice channel using in-band techniques; preferably including a payload in the polling message that identifies the target destination. In response, the remote wireless unit initiates a packet data session with the target destination.

Abstract: The present invention provides a method of controlling Wireless LAN (WLAN) medium access using Pseudo-Time Division Multiplexing (PTDM) to improve the Quality of Service (QoS) of the WLAN. The method includes the first step of a Mobile Terminal (MT) acquiring QoS information, which relates to a voice frame to be transmitted, from an upper layer; the second step of the MT exchanging a frame, including the QoS information, with the AP and being allocated QoS slot (QSLOT) information by the AP; the third step of dividing an RF link section between the MT and the AP by the creation period of the voice frame; and the fourth step of transmitting the voice frame in the creation period of the voice frame using the allocated QSLOT information.

Abstract: A method and apparatus for optimizing a distributed polling system in a network comprising a plurality of nodes. The method includes identifying bandwidth constraints on polling traffic for each of the plurality of nodes. Selecting, from a plurality of unpolled nodes within the plurality of nodes, at least one poller node according to a maximum number of unpolled nodes assignable to each of the at least one poller node without violating bandwidth constraints, and respectively assigning the unpolled nodes as pollee nodes to the at least one poller node. The apparatus includes a central manager and a plurality of pollee nodes coupled to at least one poller node via at least one routing path. At least one aggregating node is coupled to the at least one poller nodes, where the aggregating node is further coupled to the central manager.

Abstract: A scheduler for a wireless network including N wireless stations having N bandwidth parameters, respectively, comprises a framing module that generates a schedule frame including schedule slots. An assigning module assigns N sets of TxOps to the N wireless stations based on the N bandwidth parameters, respectively. Each of the schedule slots includes zero or one transmission opportunity (TxOp) for each of the N wireless stations. A polling module polls the N wireless stations based on the TxOps defined in respective ones of the N sets of TxOps.

Abstract: Provided is a real-time polling service (rtPS) class of an IEEE 802.16/WiBro system. An rtPS scheduling method of the IEEE 802.16/WiBro system includes subscriber station (SS) located in a network where the IEEE 802.16/WiBro system is realized inserting a timestamp indicating time information when uplink data is transmitted from an application layer of the SS into the uplink data; and after the SS receives polling from a base station (BS), comparing the timestamp inserted into the uplink data and a current time, and, if a difference between the timestamp and the current time is greater than a predetermined period of time, firstly dropping the uplink data.

Abstract: An apparatus, system, and method are disclosed for implementing failover in a polling adapter without support from an application server. A priority list is stored as part of an adapter configuration that specifies the server names that will participate in a group cluster. Adapters associated with the servers, in addition to accessing the event table when active, access a failover table which contains information about which adapter is currently active and when it last polled the event table. When a preconfigured failover interval has elapsed since the last poll of the event table by the active adapter, a next highest priority takes over the processing duties by polling the event table and logging its last poll time in the failover table.

Abstract: Methods and systems for controlling a personal area network access device are disclosed herein and comprise receiving at least one Bluetooth® event by a Bluetooth® device. A line speed used by the Bluetooth® device may be controlled based on the received Bluetooth® event. The line speed utilized by the Bluetooth® device may be dynamically adjusted based on the received Bluetooth® event associated with said Bluetooth device. The line speed may be dynamically adjusted utilizing a line speed algorithm. The line speed algorithm may comprise a variable bit rate coding algorithm. Encoded data may be transmitted by the Bluetooth® device utilizing the line speed. The encoded data may comprise encoded audio data. The line speed may be controlled based on a current line speed of the Bluetooth® device.

Abstract: A method for triggering a poll function in a transmitter of a wireless communications system includes triggering the poll function for polling status of a receiver, and a radio link control entity of the transmitter supporting a “Last PDU” trigger and a “Poll retransmission timer” trigger, and not supporting a “Periodic Timer” trigger.

Abstract: A method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices, the method comprising utilizing a tree search method to attempt to identify individual ones of the multiple wireless identification devices so as to be able to perform communications, without collision, between the interrogator and individual ones of the multiple wireless identification devices, a search tree being defined for the tree search method, the tree having multiple nodes respectively representing subgroups of the multiple wireless identification devices, wherein the interrogator transmits a command at a node, requesting that devices within the subgroup represented by the node respond, wherein the interrogator determines if a collision occurs in response to the command and, if not, repeats the command at the same node.