HK1147005A - Methods for intra base station handover optimizations - Google Patents

Description

Method for optimizing handover in base station

Cross reference to related applications

This patent application claims priority to provisional application No.60/976385 entitled "E-NODE-BHANDOVER METHODS AND SYSTEMS" filed on 9/28/07 and assigned to the assignee of the present application, which is expressly incorporated herein by reference.

Technical Field

Aspects of the present application relate to wireless communications devices and, more particularly, to systems and methods for optimizing intra-node handover scenarios.

Background

Wireless communication systems are widely deployed to provide various types of communication; for example, voice and/or data may be provided via such wireless communication systems. A typical wireless communication system or network may enable multiple users to access one or more shared resources (e.g., bandwidth, transmit power, etc.). For example, the system may utilize various multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and so on.

Generally, wireless multiple-access communication systems are capable of supporting communication for multiple mobile devices simultaneously. Each mobile device is capable of communicating with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations.

Wireless communication systems often employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast, and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to a mobile device. Mobile devices within the coverage area of such base stations can be employed to receive one, more than one, or all of the data streams carried by the composite stream. Similarly, a mobile device can transmit data to a base station or another mobile device.

Optimization of network coverage and quality of service is a constant goal for wireless network operators. Superior coverage and quality of service results in enhanced user experience, greater throughput, and ultimately increased revenue. One way to achieve good coverage and quality of service is by improving network efficiency. For purposes of this specification, handover or handoff may refer to both a handoff from a base station to another base station and a handoff from a base station to the same base station. In addition, the handover may be initiated by the network or the mobile terminal. The terminal may initiate a handover according to the principles of forward handover or re-establish a connection with the appropriate base station after experiencing an interruption. In addition, handovers may be performed to support user mobility in a wireless system, or to provide load balancing, or to facilitate various reconfigurations of connections or to facilitate handling of unexpected error conditions. Unfortunately, current techniques do not improve network performance efficiency through handover optimization within the base station.

Disclosure of Invention

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and thus, is not intended to identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

The present disclosure provides for optimization of handovers within a base station. In some aspects, a method for performing a handover in a wireless communication system is disclosed that includes determining whether an intra-base station handover or an inter-base station handover is to be performed, and performing the handover without resetting at least one of user plane communication protocols.

In other aspects, a base station is disclosed that includes wireless transmit and receive circuitry, and switching circuitry coupled to the wireless transmit and receive circuitry to determine at least one of whether an intra-base station or an inter-base station handover is to be performed by a UE or whether at least one of user plane communication protocols is not reset if an intra-base station handover is to be performed.

According to other aspects, a User Equipment (UE) is provided that includes radio transmission and reception circuitry, and handover circuitry coupled to the radio transmission and reception circuitry to perform a handover without resetting at least one of RLC, RoHC, and PDCP layers if an intra-base station handover is to be performed.

In one or more other aspects, a computer program product for handover in a wireless communication network is disclosed, comprising a computer-readable medium comprising code for performing a handover when an intra-base station handover is to be performed without resetting at least one of RLC, RoHC, and PDCP layers; and code for performing a handover and resetting at least one of RLC, RoHC, and PDCP layers when an inter-base station handover is to be performed.

In other aspects, an apparatus is disclosed that includes means for performing a handover when an intra-base station handover is to be performed without resetting at least one of RLC, RoHC, and PDCP layers; and means for performing a handover and resetting at least one of RLC, RoHC, and PDCP layers when an inter-base station handover is to be performed.

To the accomplishment of the foregoing and related ends, the one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more embodiments. These aspects are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed and the described embodiments are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 illustrates an exemplary multiple access wireless communication system in accordance with an aspect of the subject specification.

Fig. 2 illustrates an example generalized component block diagram of a communication system in accordance with an aspect of the subject specification.

Fig. 3 illustrates an example wireless communication system in accordance with an aspect of the subject specification.

Fig. 4 illustrates an example wireless communication system in accordance with an aspect of the subject specification.

Fig. 5 is an example wireless communication system that illustrates user plane stack protocols in accordance with an aspect of the subject specification.

Fig. 6 illustrates an example wireless communication system in accordance with an aspect of the subject specification.

FIG. 7 is a flow diagram illustrating a generalized methodology of assisting handover optimization in accordance with an aspect of the subject specification.

FIG. 8 illustrates an example apparatus to implement one or more embodiments disclosed herein.

Fig. 9 is an illustration of an example system that facilitates optimizing handover within a base station in accordance with an aspect of the subject specification.

Detailed Description

Embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that such embodiment(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

As used in this application, the terms "component," "module," "system," and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the internet with other systems by way of the signal).

Moreover, various embodiments are described herein in connection with an access terminal. An access terminal can also be called a system, subscriber unit, subscriber station, mobile, remote station, remote terminal, mobile device, user terminal, wireless communication device, user agent, user device, or User Equipment (UE). An access terminal may be a mobile telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, a computing device, or other processing device connected to a wireless modem. Furthermore, various embodiments are described herein in connection with a base station. A base station may be utilized for communicating with access terminals and may also be referred to as an access point, a node B, an enhanced nodeb (enb), or some other name.

Furthermore, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., Compact Disk (CD), Digital Versatile Disk (DVD), etc.), smart cards, and flash memory devices (e.g., EPROM, card, stick, key drive, etc.). In addition, various storage media described herein can represent one or more devices and/or other machine-readable media for storing information. The term "machine-readable medium" can include, without being limited to, wireless channels and various other media capable of storing, containing, and/or carrying instruction(s) and/or data.

Moreover, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The techniques described herein may be used for various wireless communication networks such as Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal (OFDMA) networks, single carrier FDMA (SC-FDMA) networks, and the like. The terms "network" and "system" are often used interchangeably. A CDMA network may implement radio technologies such as universal terrestrial radio access ("UTRA"), CDMA2000, and so on. UTRA includes wideband CDMA (W-CDMA) and Low Chip Rate (LCR). 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). OFDMA networks may implement methods such as evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-And so on. UTRA, E-UTRA, and GSM are described in the literature for an organization named "third Generation partnership project" (3 GPP). CDMA2000 is described in a document entitled "third generation partnership project 2" (3GPP 2). These radio technologies and standards are well known in the art.

Referring now to fig. 1, a wireless communication system 100 in accordance with the present innovation is shown. System 100 comprises a base station 102, which base station 102 can comprise multiple antenna groups. For example, one antenna group can include antennas 104 and 106, another group can include antennas 108 and 110, and an additional group can include antennas 112 and 114. Two antennas are shown for each antenna group; however, more or fewer antennas may be used for each group. Base station 102 may also include a transmitter chain and a receiver chain, each of which may in turn comprise a plurality of components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc.), as will be appreciated by one skilled in the art.

Base station 102 may communicate with one or more mobile devices, such as mobile device 116 and mobile device 122; however, it is to be appreciated that base station 102 can communicate with substantially any number of mobile devices similar to mobile devices 116 and 122. Mobile devices 116 and 122 can be, for example, cellular phones, smart phones, laptops, handheld communication devices, handheld computing devices, satellite radios, global positioning systems, PDAs, and/or any other suitable device for communicating over wireless communication system 100. As depicted, mobile device 116 is in communication with antennas 112 and 114, where antennas 112 and 114 transmit information to mobile device 116 over a forward link 118 and receive information from mobile device 116 over a reverse link 120. In addition, mobile device 122 is in communication with antennas 104 and 106, where antennas 104 and 106 transmit information to mobile device 122 over a forward link 124 and receive information from mobile device 122 over a reverse link 126. In a Frequency Division Duplex (FDD) system, forward link 118 can utilize a different frequency band than that used by reverse link 120, and forward link 124 can employ a different frequency band than that employed by reverse link 126, for example. Further, in a Time Division Duplex (TDD) system, forward link 118 and reverse link 120 can utilize a common frequency band and forward link 124 and reverse link 126 can utilize a common frequency band.

Each group of antennas and/or the area in which they are designated to communicate can be referred to as a sector of base station 102. For example, antenna groups can be designed to communicate to mobile devices in a sector of the areas covered by base station 102. In communicating over forward links 118 and 124, the transmitting antennas of base station 102 can utilize beamforming to improve signal-to-noise ratio of forward links for mobile devices 116 and 122. This may be accomplished, for example, by using a precoder to direct the signal in a desired direction. Also, while base station 102 utilizes beamforming to transmit to mobile devices 116 and 122 scattered randomly through an associated coverage, mobile devices in neighboring cells may be subject to less interference than a base station transmitting through a single antenna to all its mobile devices. Further, in one example, mobile devices 116 and 122 can communicate directly with each other using peer-to-peer or ad hoc (ad hoc).

According to an example, system 100 can be a multiple-input multiple-output (MIMO) communication system. Moreover, system 100 can utilize substantially any type of duplexing technique to divide communication channels (e.g., forward link, reverse link …), such as FDD, TDD, etc. Further, system 100 may be a multi-bearer (bearer) system. The bearer may be an information path with well-defined capacity, delay, error rate, etc. Mobile devices 116 and 122 can each serve one or more radio bearers. The mobile devices 116 and 122 can employ an uplink rate control mechanism to manage and/or share uplink resources among one or more radio bearers. In one example, mobile devices 116 and 122 can utilize a token bucket mechanism to service radio bearers and enforce uplink rate limits.

As illustrated, each bearer may have an associated Prioritized Bit Rate (PBR), Maximum Bit Rate (MBR), and Guaranteed Bit Rate (GBR). Mobile devices 116 and 122 can serve radio bearers based at least in part on the associated bit rate values. The bit rate value can also be used to calculate the queue length for each bearer taking into account PBR and MBR. The queue length may be included in the uplink resource requests sent by the mobile devices 116 and 122 to the base station 102. Base station 102 can schedule uplink resources for mobile devices 116 and 122 based on the respective uplink requests and included queue lengths.

Fig. 2 is a block diagram of the general components of a transmitter system 210 (also known as an access point or base station) and a receiver system 250 (also known as an access terminal) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a Transmitter (TX) data processor 214.

In an embodiment, each data stream is transmitted over a respective transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream can then be modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which MIMO processor 220 may further process the modulation symbols (e.g., for OFDM). TX MIMO processor 220 then processes the data to N_TA plurality of transmitters (TMTR)222a through 222t provide N_TA stream of modulation symbols. In a particular embodiment, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Then respectively from N_TN transmitted from transmitters 222a through 222t by antennas 224a through 224t_TA modulated signal.

At the receiver system 250, from N_REach antenna 252a through 252r receives the transmitted modulated signal and provides a received signal from each antenna 252 to a respective receiver (RCVR)254a through 254 r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

RX data processingThe processor 260 then proceeds from N based on the particular receiver processing technique_RA receiver 254 receiving N_RA received symbol stream is processed to provide N_TA stream of "detected" symbols. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by RX data processor 260 is complementary to that performed by TX MIMO processor 220 and TX data processor 214 at transmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix coefficients portion and a rank value portion.

The reverse link message may comprise various information regarding the communication link and/or the received data stream. The reverse link message is then processed by a TX data processor 238, modulated by a modulator 280, conditioned by transmitters 254a through 254r, and transmitted back to transmitter system 210, TX data processor 238 also receives traffic data for a number of data streams from a data source 236.

At transmitter system 210, the modulated signals from receiver system 250 are received by antennas 224, conditioned by receivers 222, demodulated by a demodulator 240, and processed by a RX data processor 242 to extract the reserve link message transmitted by receiver system 250. Processor 230 then determines which pre-coding matrix to use for determining the beamforming weights then processes the extracted message.

Fig. 3 illustrates an exemplary wireless communication system 300 for supporting several users in accordance with an embodiment of the present innovations. For example, as shown in fig. 3, the system 300 provides communication for a plurality of cells 302, e.g., macro cells 302 a-302 g, each of which is served by a corresponding Access Point (AP)304, e.g., APs 304 a-304 g. Each cell may be further divided (e.g., using directional antennas) into one or more sectors. Throughout the system, various Access Terminals (ATs) 306, including ATs 306 a-306 k, may also be referred to interchangeably as User Equipment (UE) or mobile stations, are dispersed. For example, each AT306 can communicate with one or more APs 304 on a Forward Link (FL) and/or a Reverse Link (RL) AT a given moment, depending on whether the AT is active and in soft handoff. The wireless communication system 300 may provide service over a large geographic area, for example, the macro cells 302 a-302 g may cover several adjacent blocks.

It will be appreciated that the terms "sector" and "cell" are not distinct functions for various different communication standards, such as some standards set by the body of the 3GPP standards. Thus, each node B may be considered to support multiple cells.

Referring now to fig. 4, an example wireless communication system 400 in accordance with an aspect of the subject innovation is illustrated. Node B344 is shown supporting three independent cells 304-a, 304-B, and 304-C. Thus, a handover will occur when a particular UE 334 moves from cell 304-B to cell 304-A, for example, when the UE 334 moves from an area served by node B344 to an area served by node B346. For purposes of this disclosure, a handover between two cells served by two independent node bs will be referred to as an "inter-node handover", while a handover between two cells served by a single node B will be referred to as an "intra-node B handover".

It can be appreciated that not distinguishing the type of handover may result in inefficient resource allocation. For example, as a message travels from a communication framework (e.g., the internet, etc.) to the UE 334, such message will undergo a transmission from the Internet Protocol (IP) to the Packet Data Convergence Protocol (PDCP) to the Radio Link Control (RLC) to the physical layer protocol data unit. During such transmission, each IP packet may be divided into several small RLC PDUs in order to match the capacity available to that user. The PDCP, RLC, MAC and physical layer are reset at handover, and therefore, all IP PDUs which are not completely transmitted need to be started again from the beginning. In addition, protocols that maintain state, such as the Header Compression (HC) algorithm hosted in the PDCP, will need to regenerate their state, thereby encountering a problem of inefficient compression. Further, although not required, a change in the encryption key may also be triggered. Robust header compression (RoHC) is an exemplary HC protocol used in EUTRA. RoHC is used below as an example of all HC protocols.

Optimization of the intra-node B handover situation is achievable because almost all communication contexts (contexts) associated with the UE 344 PDCP, RLC and MAC remain in the same physical location. Depending on the implementation, at least a portion of the software operates all cells in the eNB. As discussed in more detail below, in this case, intra-node B handover may be optimized to provide one or more of the following possible benefits: no reset at the PDCP layer and RLC layer is necessary, no re-ordering function associated with PDCP "handover" needs to be enabled (since RLC is persistent and re-ordered when necessary); there is no need to exchange PDCP SN status on the downlink and uplink (since all status is saved in RLC), no new security key set needs to be installed and no reset at the RoHC layer is required.

Optimizing intra-node B handovers can maximize user plane efficiency during handovers with limited complexity. The persistent RLC state enables optimal radio performance where partially transmitted and/or received SDUs do not need to be retransmitted after handover. In addition, the persistent RLC state can allow the system to not use PDCP handover related functions that may use additional resources on the air interface and may delay transmission of user plane data. Furthermore, since header compression continues after handover, the persistent PDCP environment can significantly save IP header overhead, which is very useful during the first time of RoHC environment setup when IP/UDP/RTP header overhead is higher. This is particularly useful on the uplink for UEs at the far edge of the cell. The new security key set needs to be installed because the PDCP sequence number may be reset at handover. Reusing PDCP sequence numbers with the same key may not be secure in terms of ciphering. However, if PDCP is not reset at handover, there is no need to derive, retrieve and use new keys.

Referring now to fig. 5, an example wireless communication system 500 illustrating user plane stack protocols is illustrated in accordance with an aspect of the subject innovation. System 500 includes UE 502 and eNB 504. The UE 502 and eNB504 can be capable of exchanging, transmitting, or otherwise communicating via one or more protocols including a Packet Data Conversion Protocol (PDCP)506, a Radio Link Control (RLC)508, a Medium Access Control (MAC)510, and/or a physical layer (PHY) 512.

The PDCP 506 provides ciphering and integrity protection for messages passed between the UE 502 and the eNB 504. In addition, the PDCP 506 provides a method for header compression and may participate in handover to provide lossless communication and in-order transmission. RLC508 provides for orderly and lossless transmission due to automatic repeat request (ARQ). ARQ, which includes a request for the sender to resend a packet, is issued when one or more packets are lost. RLC508 may have one or more transmission modes (e.g., often modes), including an Acknowledged Mode (AM) that requests retransmission of packets, an Unacknowledged Mode (UM) that does not use any retransmission requests, and a transparent mode that is most commonly used for signaling. RLC508 operates on a packet-by-packet basis. For example, a group of packets 1, 2, and 3 may comprise a single IP packet. If packets 1 and 3 are successfully received but packet 2 is missing or lost during transmission, then RLC508 may issue an ARQ, allowing the sender to resend packet 2. It can be appreciated that if the RLC is reset during handover, the benefit of having sent packets 1 and 3 will be lost and twice as many bits will be sent. The MAC 510 controls the scheduling and sharing of the subject medium. The PHY 512 translates communication requests from a data link layer (not shown) into hardware-specific operations to affect transmission or reception of electromagnetic signals.

The protocols 506-512 have states during operation of the system 500. However, during most any type of (e.g., inter-node or intra-node B) handover, the system 500 typically resets the aforementioned protocols, including at least a portion of the PDCP 506, RLC508, MAC 510, and PHY (512). The protocol is reset to avoid transitioning the communication environment from the first eNB to the second eNB. It can be appreciated that during an intra-node B handover, where the communication environment is in the same physical location (e.g., the same eNB), a reset protocol may be unnecessary and inefficient.

Referring now to fig. 6, an example wireless communication system 600 illustrates communication between an eNB 602 and an Evolved Packet Core (EPC) 601. EPC 601 is a central component in a Long Term Evolution (LTE) access network. It is to be appreciated that the illustrated LTE access network is only one example of how the present innovations may be utilized, and it will be apparent to those skilled in the art that the systems and methods discussed herein may be applied to a variety of network types.

EPC 601 includes Mobility Management Entity (MME)604, serving gateway (S-GW)606, and PDN gateway (P-GW) 608. The MME 604 is a control node for the LTE access network, responsible for idle mode UE tracking and paging procedures, including retransmissions. The MME 604 participates in the bearer activation/deactivation process and is also responsible for selecting the S-GW606 for the UE at initial attach and during intra-node B handover. The MME 604 is responsible for authenticating users and non-access stratum (NAS) security signaling is terminated at the MME 604. It is also responsible for generating and assigning temporary identities to UEs, checking the authorization of the UEs to use the service provider's Public Land Mobile Network (PLMN), and enforcing UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS security signaling and handles security key management.

The S-GW606 routes and forwards SDUs while also acting as a mobility anchor for the user plane during inter-node handovers. For idle state UEs, the S-GW606 terminates the DL data path and triggers paging when DL data arrives at the UE. The S-GW606 manages and stores the UE environment (e.g., parameters of IP bearer service, network internal routing information).

The P-GW 608 provides the UE with a connection to an external packet data network as an ingress and egress point for traffic for the UE. The UE may have simultaneous connections with more than one P-GW 608 to access multiple PDNs. The P-GW 608 performs policy enforcement, packet filtering for each user, charging support, lawful interception and packet screening.

As previously described, the eNB 602 includes PDCP 612, RLC 614, MAC 616, and PHY 618. Further, eNB 602 includes Radio Resource Control (RRC) 610. RRC 610 is a control plane entity capable of instructing a UE to perform intra-node B or inter-node handover. In operation, RRC 610 can send a handover command to the UE, where the command indicates the type of handover (e.g., intra-node B or inter-node). LTE is an IP system, all packets having an IP header. For example, for voice over internet protocol (VoIP) applications, the header may include one or more IP, UDP, and/or RDP headers and payloads. Sending the header over the air via the network may be inefficient due to header size, e.g., for voice over IP (VoIP), the header to payload ratio may be approximately half to half. Accordingly, the PDCP 612 can employ one or more header compression protocols, such as robust header compression (RoHC). RoHC is a full-state (state-full) header compression protocol that can significantly reduce the header size, e.g., from about 40 bytes to about 3 to 4 bytes. Typically, RoHC is reset in a handover situation. It can be appreciated that resetting RoHC during an intra-node B handover can result in unnecessary inefficiencies due to loss of compression state at the transmitter and receiver due to resetting of the header compression protocol. Thus, maintaining persistent PDCP state can partially eliminate the need to reset RoHC when the protocol is co-located, e.g., during intra-node B handover.

In view of the exemplary systems described above, methodologies that may be implemented in accordance with the disclosed subject matter will be better appreciated with reference to the flow chart of FIG. 7. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the blocks, as some blocks may occur in different orders and/or concurrently with other blocks from what is depicted and described herein. Moreover, not all illustrated blocks may be required to implement the methodologies described hereinafter.

Fig. 7 illustrates a general methodology for intra-node B handover optimization in accordance with an aspect of the innovation. At 702, communication is established between a first node B and a UE. At 710, assuming a handover is to occur with the UE, a determination is made whether the handover is an inter-node handover or an intra-node B handover. At 720, if the handover is an inter-node handover, almost any or all of the appropriate (e.g., RLC, PDCP, RoHC, and RCDP) layers may be reset.

At 730, if the handover is an intra-node B handover, it may be determined (typically by the target node B) which protocol layers (e.g., RLC, PDCP, RoHC, and/or RCDP), if any, are to be reset. It is to be appreciated that the determination of which protocol layers are to be reset can be accomplished by a variety of techniques. For example, in one embodiment, dedicated signaling from the target node to the UE may be used to determine which layers to reset and achieve multi-level granularity. In another embodiment, dedicated signaling with reverse handover allows the target node B to indicate to the UE which layers to reset with a "transparent container" in the handover request acknowledgement. The "transparent container" may contain a field for each layer, e.g., as shown in table 1, where a bit corresponding to the field instructs the UE to reset the layer.

TABLE 1

Command	Size [ bit ]]
		RLC reset	1
Rohc reset	1
		PDCP SN switching	1
Cryptographic contract change	c

In yet another embodiment, in case the terminal initiates handover autonomously (forward handover) or due to connection re-establishment, it may be indicated by the eNB whether to reset the above protocol, or derived based on parameters indicated in the system information broadcast over the air or indicated in the present document whether to reset the above protocol. Dedicated signaling may be used at 730. The target node B may obtain the relevant context for the UE (e.g., the C RNTI of the UE in the cell where RLF occurs and the cell physical layer identity and MAC based on the key of the cell) from the source node B based on the UE identifier used in the random access procedure for resolving contention.

If the node B finds appropriate communication environment information or is able to acquire communication environment information matching the UE identity within a reasonable time, the node B may indicate to the UE that its connection can be restored. In the same message and depending on the availability of RLC/RoHC/ciphering context, the node B may either deliver information to the UE (if any) or have to reset all protocols (e.g., RLC, RoHC, ciphering status, etc.). If no suitable communication context information is found, the relevant protocol is reset.

Additionally or alternatively, unique signaling may be used to determine which protocol layers need to be reset. For example, only 1 bit of information may be used to indicate whether a set of protocols (e.g., PDCP and RLC) is reset. The UE may then be instructed not to reset these protocols during intra-node B handover, but to always reset them during inter-node B handover.

In addition, there are at least two options for informing the UE of the handover type, including a unicast handover type and a broadcast handover type. The unicast handover type specifies that at the time of handover, the target node B can determine whether the handover is intra-node B or inter-node B. This may be achieved by a single signalling bit (e.g. intra/inter eNB) which may be embedded in a transparent container in the handover request acknowledgement. The source node-B can generate and send an appropriate handover command (e.g., RRC message) to the UE. The handover command may include a transparent container received from the target node B.

During operation, the UE may determine whether to reset each protocol when accessing the target node B. Note that this signaling method still leaves the freedom to not implement any optimization, since during an intra-node B handover, the target node B may decide to indicate an "inter-node B handover" in the transparent container of the handover request acknowledgement.

In the case of connection re-establishment, the target node B can indicate intra-or inter-node B handover to the UE in a message indicating that its connection can be resumed. All layer two user plane protocols may be reset if the context does not become available. The broadcast handover type (e.g., broadcast node B identity (eNB ID)) specifies, as previously described, which protocols continue to achieve a first consensus during intra-node B handover. Furthermore, there is a need to agree that inter-node B handovers are always optimized.

In this manner, a locally unique eNBID can be broadcast on P-BCH or D-BCH, for example. At handover, the UE may determine whether an intra-node B or inter-node B handover is occurring and thus be able to set the RLC/PDCP state accordingly. This approach can be used in normal handover as well as in forward handover and connection re-establishment, since no dedicated signalling is required.

Optimizing intra-node B handovers in the foregoing manner enables several benefits without resetting all protocol layers. For example, if the RLC is not reset, the number of repeated bits sent is reduced as a result of the handover (described above). In addition, not resetting the PDCP may also reduce the amount of duplicate data due to handover. As described previously, the PDCP performs retransmission by exchanging status reports, in which the receiver notifies the sender of data that it has received and has not received. For example, the UE retransmits all packets that are not known to be acknowledged in a cumulative manner. A group of IP packets ordered from one to ten is being sent, the last packet that has been acknowledged before the handover is the fifth packet. The UE will retransmit the sixth through tenth groups, whether received or not, because the PDCP has been reset. Similarly, maintaining a constant state by the protocol can reduce the necessity of exchanging PDCP SN status on the uplink and/or downlink. Also, as previously described, not resetting the RoHC layer may improve efficiency during intra-node B handovers.

Refinement of 1-bit intra/inter-node bit switching can be achieved by identifying which protocol or component thereof is reset/not reset at the time of switching. For example, a bitmap may be used to independently indicate whether to reset the PDCP/HC/RLC/MAC for this occurrence of handover. The bitmap may be sent as part of a handover along with dedicated signaling. This enables a more flexible implementation where, for example, if the RLC context can be shared but the PDCP cannot be shared, then only the RLC state is maintained. At 732, information regarding which layers to reset and/or a simple signal (e.g., a flag) indicating that an intra-node B handover is to occur is sent to the UE. At 734, the appropriate layers are reset and/or the appropriate compression/encryption keys may be changed. At 740, any remaining handoff functions may be performed.

Referring now to fig. 8, shown is a schematic block diagram of a portable handheld terminal device 800 in which a processor 802 is responsible for controlling the overall operation of the device 800. The processor 802 is programmed to control and operate the various components within the device 800 in order to perform the various functions described herein. The processor 802 may be any of a variety of suitable processors. The manner in which the processor 802 is programmed to carry out the functions associated with the present invention will be readily apparent to those of ordinary skill in the art based on the description provided herein.

A memory 804 coupled to the processor 802 is used to store program code executed by the processor 802 and serves as a storage module to store information such as user credentials and receive transaction information. The memory 804 may be a non-volatile memory adapted to store at least a complete set of displayed information. Thus, the memory 804 may include RAM or flash memory that is accessed by the processor 802 at high speed and/or mass storage memory, such as a microdrive capable of storing gigabytes of data including text, images, audio and video content. According to one aspect, the memory 804 has sufficient storage capacity to store multiple sets of information, and the processor 802 may include a program for alternating or cycling between sets of display information.

A display 806 is coupled to the processor 802 via a display driver system 808. The display 806 may be a color Liquid Crystal Display (LCD), a plasma display, or the like. In this example, the display 806 is an 1/4 VGA display having sixteen levels of gray scale. The display 806 is used to present data, drawings, or other informational content. For example, the display 806 may display a set of customer information, may display the customer information to an operator, and may transmit the customer information over a system backbone (not shown). Further, the display 806 can display various functions that control the execution of the device 800. The display 806 is capable of displaying alphanumeric and graphical symbols.

The processor 802 and other components forming the handheld device 800 are powered by an on-board power system 810, such as a battery pack. If the power system 810 fails or is disconnected from the device 800, an auxiliary power supply 812 may be employed to power the processor 802 and to charge the on-board power system 810. The processor 802 of the device 800 induces a sleep mode to reduce current draw when an anticipated power failure is detected.

The terminal 800 includes a communication subsystem 814, the communication subsystem 814 including a data communication port 816, the processor 802 being interfaced to a remote computer using the data communication port 816. The port 816 can include at least one of Universal Serial Bus (USB) and IEEE 1394 serial communications capabilities. Other techniques may also be included, such as infrared communication using an infrared data port.

The device 800 may also include a Radio Frequency (RF) transceiver section 818 in operative communication with the processor 802. The RF section 818 includes an RF receiver 820 that receives RF signals from a remote device via an antenna 822 and demodulates the signals to obtain digital information modulated therein. The RF section 818 also includes an RF transmitter 824 for transmitting information to a remote device, for example, in response to manual user input via a user input device 826 such as a keypad or automatically in response to completing a transaction or other predetermined and programmed criteria. The transceiver section 818 facilitates communication with a passive or active transponder system, such as an RF tag with a product or item. The processor 802 signals (or pulses) the remote transponder system via the transceiver 818 and detects the return signal to read the contents of the tag memory. In one embodiment, the RF section 818 also facilitates telephone communications with the device 800. In its development, an audio I/O section 828 controlled by the processor 802 is provided to process sound input from a microphone (or similar audio input device) and audio output signals (from a speaker or similar audio output device).

In another embodiment, the device 800 may provide voice recognition capabilities such that when the device 800 is used only as a voice recorder, the processor 802 can facilitate high speed conversion of voice signals into text content for local editing and review, and/or subsequent download to a remote system, such as a computer word processor. Similarly, the device 800 may be controlled using converted speech signals rather than using manual input via the keypad 826.

Onboard peripheral devices such as a printer 830, signature panel 832 and magnetic stripe reader 834 may also be provided within the housing of the device 800 or externally via one or more external port interfaces 816.

The device 800 may also include an image capture system 836 so that a user can record images and/or short movies for storage by the device 800 and presentation by the display 806. In addition, a data table reading system 838 is included to scan the data tables. It is to be appreciated that the imaging systems (836 and 838) may be a single system capable of performing both functions.

Referring to fig. 9, illustrated is a system 900 that facilitates specifying a key set from a plurality of key sets employed in a transmission. For example, system 900 can reside at least partially within a base station, mobile device, etc. It is to be appreciated that system 900 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). System 900 includes a logical grouping 902 of electrical components that can act in conjunction. For example, logical grouping 902 can include an electrical component for handing off when an intra-base station handoff is to be performed without resetting at least one of the several layers 904. Further, logical grouping 902 can include an electrical component for handing off and resetting at least one of the number of layers when an inter-base station handoff is to be performed 906. Further, logical grouping 902 can include an electrical component for obtaining information regarding whether an intra-base station handover or an inter-base station handover is to be performed 908. Additionally, system 900 can include a memory 910 that retains instructions for executing functions associated with electrical components 904, 906, and 908. While shown as being external to memory 910, it is to be understood that one or more of electrical components 904, 906, and 908 can exist within memory 910.

The previous description of the disclosed examples is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these examples will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other examples without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the examples shown, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (29)

1. A method for handover in a wireless communication system, comprising:

judging whether to perform intra-base station handover or inter-base station handover; and

the handover is performed without resetting at least one of the user plane communication protocols.

2. The method of claim 1, the user plane communication protocol comprises at least one of a medium access control, a radio link control, a packet data convergence protocol, a header compression, or a security key.

3. The method of claim 1, further comprising performing the handover without resetting any of the user plane communication protocols if an intra-base station handover is to be performed.

4. The method of claim 2, further comprising performing the handover while resetting all of the user plane communication protocols if an inter-base station handover is to be performed.

5. The method of claim 1, further comprising sending a message to the terminal indicating the layers to be reset during the handover.

6. The method of claim 1, further comprising sending a message to a terminal indicating whether the handover is an inter-base station handover or an intra-base station handover.

7. A method for handover in a wireless communication system, comprising:

if an intra-base station handover is to be performed, performing the handover without resetting at least one of the user plane communication protocols; and

resetting at least one of the user plane communication protocols during the handover if an inter-base station handover is to be performed.

8. The method of claim 7, wherein the user plane communication protocol comprises at least one of a medium access control, a radio link control, a packet data convergence protocol, a header compression, or a security key.

9. The method of claim 7, further comprising receiving information from the target base station as to whether an intra-base station or an inter-base station handover is to be performed.

10. The method of claim 7, further comprising performing the handover without resetting any of the user plane communication protocol layers if an intra-base station handover is to be performed.

11. The method of claim 7, further comprising performing the handover while resetting all of the user plane communication protocols if an inter-base station handover is to be performed.

12. The method of claim 7, further comprising receiving an indication from the target base station indicating which, if any, of the user plane communication protocols are to be reset during the handover.

13. The method of claim 7, further comprising receiving an indication from a target base station indicating whether the handover is an inter-base station handover or an intra-base station handover.

14. A communication device, comprising:

a wireless transmitting and receiving circuit; and

switching circuitry, coupled to the wireless transmit and receive circuitry, to make at least one of the following determinations: whether the UE is to perform intra-base station handover or inter-base station handover; or whether at least one of the user plane communication protocols is not reset if an intra-base station handover is to be performed.

15. The apparatus of claim 14, wherein the base station determines whether the user plane communication protocol is to act as an inter-base station handover or an intra-base station handover based on environmental availability associated with the user plane communication protocol.

16. The apparatus of claim 14, wherein the user plane communication protocol comprises at least one of a medium access control, a radio link control, a packet data convergence protocol, a header compression, or a security key.

17. The apparatus of claim 14, wherein if an intra-base station handover is to be performed, the handover is performed without resetting any of the user plane communication protocols.

18. The apparatus of claim 14, wherein if an inter-base station handover is to be performed, performing the handover resets all of the user plane communication protocols simultaneously.

19. The apparatus of claim 14, wherein a message is sent to the terminal indicating the layers to be reset during the handover.

20. The apparatus of claim 14, wherein a message is sent to a terminal indicating whether the handover is an inter-base station handover or an intra-base station handover.

21. A wireless communication device, comprising:

a wireless transmitting and receiving circuit; and

handover circuitry, coupled to the radio transmit and receive circuitry, to perform a handover without resetting at least one of the RLC, RoHC, and PDCP layers if an intra-base station handover is to be performed.

22. The apparatus of claim 21, wherein a message is received indicating at least one layer to be reset during handover.

23. The apparatus of claim 21, wherein a message is received indicating whether the handover is an inter-base station handover or an intra-base station handover.

24. A computer program product for handover in a wireless communication network, comprising:

a computer-readable medium comprising:

code for performing an intra-base station handover without resetting at least one of RLC, RoHC, and PDCP layers if the handover is to be performed; and

code for performing an inter-base station handover if the handover is to be performed, and resetting at least one of RLC, RoHC, and PDCP layers.

25. The computer program product of claim 24, further comprising code for determining whether an intra-base station or an inter-base station handover is to be performed.

26. The computer program product of claim 24, further comprising code for receiving information regarding whether an intra-base station or an inter-base station handover is to be performed.

27. A wireless communication device, comprising:

means for performing a handover without resetting at least one of RLC, RoHC, and PDCP layers if an intra-base station handover is to be performed; and

means for performing a handover and resetting at least one of the RLC, RoHC, and PDCP layers if an inter-base station handover is to be performed.

28. The apparatus of claim 27, further comprising means for determining whether an intra-base station or an inter-base station handover is to be performed.

29. The apparatus of claim 27, further comprising means for receiving information regarding whether an intra-base station or an inter-base station handover is to be performed.