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`1289
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`Wireless Intelligent ATM Network and Protocol
`Design for Future Personal Communication Systems
`
`Fang-Chen Cheng and Jack M. Holtzman, Fellow, IEEE
`
`Abstract— This paper presents a wireless network infrastruc-
`ture for future personal communication system, which is referred
`to the wireless intelligent ATM (WIATM) network, to provide
`wireless broad-band integrated services. The WIATM network
`takes advantages of the ATM-cell relay paradigm for integrated
`services through a radio link with Quality of Service (QoS)
`guarantee. The design of the WIATM network architecture is
`an independent wireless network, which is consistent with the in-
`herent cellular/PCS network architecture, as a wireless customer
`premises equipment/network (CPE/CPN) to access the ATM
`transport network in the B-ISDN infrastructure. An independent
`network architecture design separates the wireless access net-
`work from the ATM backbone network; this provides flexibility
`for wireless resource management with low rate source codecs
`with minimal tolerable QoS considered to increase the spectral
`efficiency, and mobility support by taking advantage of the
`functionalities of the IS-41 circuit-switching handoff procedures.
`The protocol design of the air interface is to meet the QoS re-
`quirements of wireless B-ISDN services and to be compatible with
`that of B-ISDN UNI. A hybrid concatenated error control scheme
`distributed through the protocol layers is used to target individual
`QoS requirements of different services. The convolutional coding
`and interleaving in the wireless physical layer protocol are used
`to guarantee QoS of voice services. A concatenated coding with
`additional 36 bit BCH code in the wireless ATM layer, which
`replaces the VCI/VPI of the ATM header field, improves the
`QoS up to the requirement of video services. The VCI/VPI field
`in WIATM is an overlapped routing information routing with
`the address control by radio port controller, and is thus not
`needed in the wireless ATM layer protocol. The retransmission
`scheme for data service only is added in the wireless data
`link layer, which is on top of wireless AAL, to meet its QoS
`requirement. Examples of signaling flows for call registration,
`call setup, and supporting handoff are shown in the design of
`the wireless network layer protocol. The AIN (advance intelligent
`network) signaling functionalities are considered for multimedia
`service control in the access network and interconnection to the
`ATM network. A parent–child creative basic call state model
`(BCSM) for wireless integrated services is introduced in both
`call origination and termination.
`
`Index Terms— AIN, ATM, BCSM, B-ISDN, CDMA, cellular,
`error control, handoff, mobility support, multimedia, network ar-
`chitecture, PCS, protocol, signaling control, SS7, TDMA, wireless.
`
`I. INTRODUCTION
`
`RECENT studies of “wireless ATM” have focused on
`
`the communication aspects with ATM as the backbone
`transport network. Wireless ATM is considered as a wireless
`
`Manuscript received September, 1, 1996; revised April 1, 1997. This work
`was supported in part by GTE Laboratories, Waltham, MA.
`The authors are with WINLAB, Rutgers University, Piscataway, NJ 08855
`USA.
`Publisher Item Identifier S 0733-8716(97)05846-0.
`
`access network to interconnect the mobile users to the ATM
`network. Problems in wireless ATM concentrate on the effects
`of the packet mode information transport in the wireless envi-
`ronment, which is characterized by unreliable sharing access
`with finite resource and mobility. Several wireless network ar-
`chitectures [1]–[7] have been proposed to interconnect inherent
`cellular/PCS systems or wireless LAN’s to the ATM network.
`The flexibility of the radio interface design is considered
`to be compatible with existing cellular/PCS systems, and to
`provide for future multimedia services such as data, video,
`or integrated services. Other proposed wireless ATM network
`architectures [8]–[10] focus on the wireless extension of the
`B-ISDN terminals for seamless ATM connection. The air
`interface design of [8]–[10] applies ATM cell transport through
`radio link for broad-band integrated services. Modified or
`enhanced functionalities of the B-ISDN UNI (user–network in-
`terface), such as ATM and AAL layer protocols, are suggested
`to improve the wireless connectivity, which includes error
`control to improve the error performance and mobility support.
`Analytical studies in error control for wireless multimedia
`services include [2]–[4], [8], and [11]–[13]. The channel
`coding in the wireless physical layer, such as forward error
`correcting (FEC), convolutional coding, interleaving, concate-
`nated coding, multicarrier modulation and diversity reception,
`and ARQ retransmission in the link layer, are considered
`to meet the target BER of individual service requirement.
`Mobility support in wireless ATM is discussed in [14]–[21].
`Focuses of mobility support include handoff protocol design,
`rerouting for handoff, and location management. Reference
`[22] discusses the current available technology of PCS and
`ATM for the mobile multimedia scenario. Additional functions
`required in the ATM layer of the B-ISDN protocol to support
`mobility in the design of extending ATM terminals to wireless
`environments are discussed in [16].
`Also, there are several works investigating the AIN-capable
`signaling control in wireless ATM. Focuses of the AIN signal-
`ing control in wireless ATM are the design of the platforms of
`the service control and to support mobility [1], [9], [23]–[26]
`and resource management [26]. The separation of functions
`and physical equipment in the AIN service control provides
`sophisticated and efficient network control for multimedia
`services in the design of the wireless ATM network. There
`are a number of other references on wireless ATM as well.
`Our objective is to design a wireless network to provide
`wireless B–ISDN services for future personal communication
`systems. The design of the WIATM network combines three
`reference models of inherent networks; they are the cellu-
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`lar/PCS network (wireless), AIN (intelligent), and the ATM
`network (ATM)—hence the terminology WIATM. The evolu-
`tion from ISDN to B-ISDN emphasizes issues of high-speed
`network design for broad-band integrated traffic with highly
`diverse service rates. The ATM network features high-speed
`information transport and high efficiency of the switching
`capacity for the transport of broad-band integrated traffic by
`combining the advantages of traditional circuit-switching and
`packet-switching networks. The limitation of resources, the
`unreliable radio channel, and the mobility of users characterize
`wireless communication. Thus, the requirement of QoS is
`redefined with more tolerance toward errors in cellular/PCS.
`Communication techniques, such as modulation, channel cod-
`ing, diversity reception, and sophisticated antennas, are imple-
`mented to battle the received signal degradation through the
`unreliable radio link and to increase the system capacity. The
`enhanced signaling protocol in UNI is designed to support the
`mobility in cellular/PCS. The developing AIN is considered
`for signaling control to enhance the capability of user–network
`access for wireless multimedia services. In particular, the AIN
`signaling control is highly feasible for the target personal com-
`munication system which demands a sophisticated network
`signaling control mechanism for user–network interaction and
`mobility. Further, AIN-capable signaling control is included
`in the ITU standard B-ISDN signaling protocol. In general,
`emphasis is placed on taking advantage of well-developed
`standards where appropriate.
`The system design of the WIATM network starts by laying
`out the overall picture of the wireless network architecture. The
`interworking between wireless ATM and the ATM backbone
`network is discussed next for end-to-end information flow. In
`particular, the mobility support in wireless ATM strongly con-
`nects to the wireless network architecture and the interworking
`functionalities. Henceforth, a clear picture of the role of
`WIATM in the B-ISDN infrastructure is displayed. The design
`of the air interface targets improvement of the radio connectiv-
`ity, which includes the error performance and mobility support.
`A digital signaling protocol in the air interface and AIN-
`type signaling control are considered for multimedia personal
`communication systems. The role of wireless ATM and its
`general issues are presented in Section II. The architecture of
`the WIATM network and internetworking are shown in Section
`III. The air interface design for user information transport
`and guarantee QoS is presented in Section IV. The signaling
`control protocol to support mobility is shown in Section V,
`and concluding remarks are given in Section IV.
`
`II. WHY WIRELESS ATM?
`
`A. The Role of Wireless ATM
`
`Wireless ATM is considered as the wireless subdomain of
`the B-ISDN infrastructure shown in Fig. 1. The subdomain is
`in the sense of extending the user–access network, which is in
`terms of the customer premise equipment (CPE) of the ATM
`network, to the wireless environment.
`From Fig. 1,
`the ATM network is the backbone trans-
`port, and the SS7 signaling network provides global number
`
`translation for ATM network end-to-end virtual circuit setup.
`The CPE is considered as a subscriber loop, which has
`routing capability inside the loop and provides the mobile
`user with access to the ATM network. The CPE’s include
`the telephone network, wide-area network (WAN), local-area
`network (LAN), private ATM network or B-ISDN terminals,
`and the wireless network. The network termination (NT) is a
`transport network endpoint, which contains the interworking
`functions to interconnect the CPE’s and the ATM network.
`The interworking functions contain the signaling capability to
`perform routing in the ATM network and user–network access
`inside the CPE. The well-known ATM Forum is organized
`to standardize the physical equipment and the connection
`specifications, such as the protocol design routing algorithm
`(e.g., P-NNI) and mobility support, inside the domain of the
`CPE. Wireless ATM has the role of a wireless access network,
`as wireless CPE of the ATM network.
`
`B. Wireless Transport Mechanism for B-ISDN Services
`
`“Wireless ATM” originates by applying the ATM-type trans-
`port mechanism through the radio link for B-ISDN services.
`Advantages of the ATM-cell relay paradigm are the flexibility
`of the resource management of the bursty mixed traffic, and
`the QoS control and guarantee of each traffic. The mixed traffic
`is output of the B-ISDN services, which are characterized by
`integrating the highly diverse rate-bearer services, such as low-
`rate voice and data services, and high-rate data, image, and
`video services. Also, the B-ISDN services demand variable
`measure of the performance parameters, such as delay tol-
`erance, delay jitter, and bit-error rate. Hence, wireless ATM
`exploits the ATM-cell transport mechanism on the radio design
`for the B-ISDN services through the radio link.
`There are several alternatives for the radio design for
`B-ISDN services. For simplicity, the B-ISDN bearer services
`are categorized into high- and low-rate services. Fig. 2 shows
`three alternatives for the radio design for B-ISDN services. The
`mapping and set partitioning and the signal block diagram for
`three alternatives are shown in columns (A) and (B) of Fig. 2,
`respectively. The set partition presents resource sharing (radio
`with MAC) or logic separation (bearer services). Mapping is
`to integrate diverse bearer services to a radio.
`The three alternatives in Fig. 2 are the following.
`
`a) Traditional circuit switching—The radio contains two
`separate sets of access control, each of which responds
`for a fixed rate-bearer service. The two-set access con-
`trol could be two different frequency carriers (ODFM),
`two different frequency bands (FDMA), two time slots
`(TDMA), or two spreading codes (CDMA).
`b) Segment circuit switching—The radio contains a low-
`rate radio channel subset as a unit. The number of units
`is different to distinguish between low-rate and high-
`rate services. The small unit could be subband (FDMA),
`small time slot (TDMA), multiple codes (CDMA), or
`hybrid.
`c) ATM—The high-rate and low-rate services are cate-
`gorized into five classes of services, with each class
`having different measures of performance parameters.
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`Fig. 1. B-ISDN infrastructure.
`
`Each class of services with variable rate is segmented
`into fixed size cells. The radio integrates all cells.
`The radio resource in (a) has to be divided into two parts
`for high-rate and low-rate access control. Hence, the resource
`utilization in (a) is low and inefficient. In (b),
`the radio
`resource is managed based on the demanding numbers of units.
`The physical equipment in (b) requires multiple numbers of
`parallel receivers or series time slots. The spectral efficiency
`in (b) decreases as the source gets highly bursty. Also, the
`admission control is inflexible in (b). For the ATM-cell relay
`paradigm in (c), the high-speed radio spatially multiplexes all
`cells from each class of service. The bursty characteristic of
`the multimedia source reflexes on the transport mechanism,
`and is best for the performance control. The radio resource
`utilization is high and efficient in (c).
`
`C. Issues in Wireless ATM
`
`Two factors affect the cost of the network infrastructure;
`they are the location of the ATM network termination point
`(NT), which supports full capability of SS7 for number trans-
`lation to set up ATM end-to-end virtual connections, and the
`distribution of the air interface functionalities. It is costly on
`
`the wireless side to support SS7’s capabilities to interpret
`the global network topology and to set up the end-to-end
`connection. The functional distribution between the mobile
`switches and base stations of the air interface design is also
`cost effective.
`The next
`issue is how to increase the wireless system
`capacity, which is in terms of optimizing spectral efficiency for
`integrated narrow-band/broad-band traffic. Specifying lower
`rate-bearer services with minimal
`tolerable QoS, such as
`low-rate voice codec or low-resolution video, for a wireless
`network with given available bandwidth can increase the
`number of users in the system. The effect of the overhead
`redundancy, which is the ratio of the information field and
`the total packet
`length,
`is also another issue in resource
`management. All of the traffic parameters, such as QoS
`parameters, ATM traffic descriptor, and AAL parameters, are
`subject to change based on the new specified lower rate-bearer
`services, necessitating the modification of the protocols of the
`ATM layer, AAL, and network layer because these protocols
`contain the traffic parameter elements which are mandatory.
`Most notable in wireless ATM is how to improve error
`performance through the unreliable radio link and guarantee
`the QoS of individual service. The design of the error control
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`(a)
`
`(b)
`
`(c)
`
`transformation for both high-rate and low-rate bearer channels to radio channels. (b) Direct
`Fig. 2. Radio design for B-ISDN services. (a) Direct
`transformation for high-rate and low-rate bearer channels to parallel low-rate radio channels. (c) Two-step transformation for high-rate and low-rate
`bearer channels to high-speed radio channels.
`
`mechanism and the selection of modulation, coding, receivers,
`diversity, and MAC protocol provide different solutions for
`service performance control. The error control schemes, by in-
`troducing redundancy, which increases the service bandwidth,
`also relate to the system capacity.
`
`The signaling control and how to support mobility in
`wireless ATM are other issues. For signaling control,
`the
`enhancement of the ITU Q.2931 protocol is required. The
`specifications of the bearer capability and traffic parameters
`for wireless services need to be added. The decision of the
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`connection type to support mobility has a significant impact
`on the system design, especially for ATM-type cell transport.
`The call forwarding scheme or new connection during the
`interswitch handoff are two alternatives, and are based on the
`design of a wireless network architecture.
`
`III. THE WIRELESS ATM NETWORK ARCHITECTURE
`
`The wireless network architecture contains the network
`structure design,
`the distribution of functionalities, the air
`interface design and its protocol stack, and the design of the
`interworking functions to interconnect to the ATM transport
`network. The distribution of the functional blocks in the
`wireless network is based on the network control strategy to
`determine the capabilities for user-to-network and network-
`to-network access. The air interface design delivers the re-
`quirement of the reliable radio connectivities for information
`transport and signaling control based on the characteristics of
`the wireless environment. The interworking functions convert
`the information elements in the wireless network to standard
`formats of the ATM network. In addition, it also connects the
`wireless signaling control elements to the signaling network
`for settlement of the end-to-end connection.
`
`A. Issues in Wireless Network Architecture
`Design and Mobility Support
`
`The design strategy of the WIATM network architecture
`is stretched out from Fig. 1. In Fig. 1, wireless ATM is
`a wireless access network (W-CPE) to interconnect to the
`ATM backbone network. Since the wireless communication
`has its own specific characteristics, the WIATM network is
`designed to have an independent network architecture, which
`is same as the inherent cellular/PCS network and is also
`shown in [1] and [3]. An independent network architecture
`design separates the wireless access network from the transport
`network. The separation between the access network and the
`transport network enables flexible system design, best for
`mobile communication. The advantages of an independent
`network architecture include a lower rate voice source codec
`being used to optimize the bandwidth utilization, flexible
`system design to improve the performance through unreliable
`radio link, and call admission control to guarantee the QoS of
`each user. In addition, the QoS specification in a cellular/PCS
`system is set at
`the minimal
`tolerable quality to further
`increase the system capacity. In particular, the flexibility of the
`independent network architecture design enables customized
`peer-to-peer protocols running and routing the algorithm inside
`the wireless network, such as a TCP/IP protocol for the
`wireless ATM LAN. Also shown in Fig. 1, the wireless CPE
`design requires minimal signaling capability for routing and
`mobility support inside the wireless subscribers loop (W-CPE),
`including connection setup during handoff and interconnection
`to the ATM network. This implies that no modification is
`required for the B-ISDN NNI protocols to support mobility in
`the wireless ATM network. The drawback of the independent
`architecture is that the complexity of the interworking function
`increases, where the information format is converted and the
`mobility of wireless user access is detected and supported.
`
`We summarize the WIATM network architecture and sev-
`eral previous works [1], [8], [9], [3] in Fig. 3. The pro-
`posed network architectures in Fig. 3 are designed based on
`a cellular-like system environment, which is different from
`that of a wireless ATM LAN. Reference [1] proposes an
`ATM access network with packet handler for information
`transport of the inherent cellular/PCS system. The proposed
`network architecture in [8] is to extend the ATM terminals
`with enhancement to wireless environment for future PCN’s.
`An ATM-UNI compatible air interface with additional PCN
`overhead is designed for the wireless access identification
`and error control. Reference [9] proposes a subnet structure
`of a wireless ATM network to integrate wireless access with
`the ATM network and B-ISDN UNI compatible air interface
`design. In [3], an independent wireless access network design
`provides flexibility in frame structure conversion between the
`CDMA frame and the ATM cell. A flexible radio interface
`design can support an IS-95 CDMA terminal and the ATM-
`type terminals, with variable rate up to 256 kbit/s. Two hybrid
`ARQ error control schemes also mentioned in [3] to improve
`the QoS of the nonreal-time services. The thick solid lines in
`Fig. 3 show the connections at the worst scenario during the
`interswitch handoff stage in each proposed architecture. New
`end-to-end connections are required in the architectures of [8]
`and [9]. A preestablished VCI/VPI connection for fast handoff
`is proposed in [1]. An independent network architecture design
`in WIATM enables us to apply the call forwarding strategy in
`IS-41 [27] for the interswitch handoff. The call forwarding is
`based on maintaining the connection from the ATM network
`at an anchor switch and setting up a tandem connection to the
`new switch inside the wireless network during the interswitch
`handoff. The call forwarding mechanism for interswitch hand-
`off in wireless ATM reduces the cell loss caused by additional
`delay from user mobility and call control complexity, such
`as storage of control state parameters which include handoff
`state and billing information.
`
`B. Error Control in WIATM
`
`The BER and the delay tolerance are two important indexes
`of the QoS in wireless communication. The QoS parameters,
`which consist of cell loss ratio, cell loss priority, mean delay,
`and variance of delay, are specified during the ATM connection
`establishment for a given level of QoS guarantee. However,
`the unreliable radio channel and limited available bandwidth
`in wireless communication restrict the QoS to the minimal
`achievable level in order to optimize the spectral efficiency.
`This implies that
`the current QoS parameters, which are
`defined based on a reliable high-speed channel, are infeasible
`for wireless ATM alone. Also,
`the limited bandwidth in
`wireless communication results in defining low rate-bearer
`services. The ATM traffic descriptor, which includes the mean
`and peak cell ratio, and the AAL parameters are subject to
`change with low rate-bearer services. The independent network
`architecture design in WIATM acknowledges the demand to
`define a separated set of QoS and traffic parameters for wire-
`less ATM. References [8] and [11] list tables of applications,
`traffic parameters, and QoS parameters for wireless multimedia
`services.
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`Fig. 3. Different approaches in the design of wireless ATM.
`
`The error control strategies from previous work focus on
`received signals combining,
`the multiple-access technique,
`channel coding, and retransmission. Reference [2] analyzes the
`system capacity, which guarantees wireless multimedia QoS
`by using different combinations of FEC coding and antenna
`diversity with maximal ratio combining through Rayleigh
`fading channel. A variable-rate FEC with fixed frame size for
`a wireless multimedia system is proposed in [28] to target
`the different BER requirement of multimedia services. TDMA
`with time-of-expiration based queue service disciplines is
`investigated to improve the QoS for further details of wireless
`multiservices in [8]. A TDMA scheme with the DFT-based
`multicarrier modulation (MCM) technique for high-rate ATM
`packet transmission is studied in [12] to reduce the intersymbol
`
`interference caused by multipath spread in indoor radio. Delay
`analysis for real-time services and hybrid channel coding for
`nonreal-time services for error control are addressed in [3].
`Cochannel interference cancellation and hybrid error control
`schemes are presented in [11] for QoS control in a DS-CDMA
`system. Reference [29] discusses QoS management schemes
`for high-rate multimedia services over low-rate CDMA bearer
`channels.
`Our error control strategy is to distribute to the peer-to-peer
`protocol layers based on the source characteristics. The error
`performance is controlled by concatenated coding in the lower
`layer protocol to satisfy the minimal requirements of the real-
`time services. The real-time services include voice and video
`services, and are delay sensitive. The error performance of the
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`Fig. 4. Air interface of the wireless intelligent ATM network.
`
`voice service is controlled by the convolutional coding and
`interleaving as an outer code in the wireless physical layer
`which agrees with the
`protocol to achieve a BER beyond 10
`QoS target of inherent cellular/PCS system design. The BCH
`forward error control (FEC) coding as an inner code in the
`wireless ATM layer protocol boosts the BER performance up
`to the minimal requirement of the video service. The additional
`ARQ is designed in the wireless data link layer protocol for the
`data services only. The data service is highly error sensitive
`and delay tolerant. The error performance of individual service
`in the broad-band integrated services meets its own minimal
`requirement through the hybrid concatenated coding scheme.
`
`IV. THE AIR INTERFACE DESIGN
`
`Our approach to wireless ATM is to take maximal advantage
`of functionalities in the B-ISDN UNI protocols, such as
`multiplexing physical channel, ATM, AAL, and Q.2931, with
`separate performance measures in wireless environments. This
`leads to our philosophy of air interface design, which is to
`accommodate the B-ISDN UNI with minimal modification
`required for the best fit in wireless ATM. The reference model
`of the air interface design are the protocol stacks of ITU
`B-ISDN UNI [30]–[38]. The air interface design is compatible
`with the protocol stack in the ATM network. Also, it captures
`the essence of the ATM-cell transport mechanism shown in Fig
`2(c) and discussed in Section II-B. Based on the consideration
`of the central control structure and minimizing the cost of the
`infrastructure, the functional distribution of the air interface
`peer-to-peer protocols in WIATM is mostly concentrated in the
`mobile switching center (MSC). The base station (BS) plays
`a role as an access point to relay information between mobile
`and MSC. The air interface protocol stack of the WIATM
`network is shown in Fig. 4. Protocol layers shown in Fig. 4
`contain a wireless data link layer (W-DL), which is in addition
`
`to that of B-ISDN to perform retransmission for the data
`services only. The air interface design shown in Fig. 4 takes
`advantage of the independent network architecture design
`mentioned in Section III to compose ATM-compatible protocol
`stacks based on the characteristics of wireless communication.
`The ATM-compatible protocol design enables flexible system
`engineering in the wireless environment without being strictly
`constrained by the B-ISDN UNI protocol, and the modification
`of the B-ISDN NNI protocol. Flexible system engineering
`includes maximizing the spectral efficiency, defining a new set
`of wireless QoS parameters, improving error control through
`radio links, and supporting mobility. The air interface design in
`Fig. 4 requires no modification of B-ISDN NNI, in particular,
`the SS7 signaling control, to support wireless features.
`
`A. Design of Wireless Physical Layer
`
`The wireless physical layer (W-PL) protocol consists of
`radio and medium access control (MAC) sublayers. From
`Section III-B, the W-PL protocol design strategy is to design
`a radio and MAC scheme which the error performance targets
`toward the minimal tolerable level of voice service (BER
`around 10
`The design and selection of the radio and the
`MAC protocol are subject to how the system capacity can
`be optimized by given available bandwidth under a fading
`channel environment. Several previous works [1]–[3], [8],
`[11], [22], [28], [12], [39–[42], [10], [7] have discussed the
`design of radio and MAC protocol for high-rate multimedia
`services. CDMA as an access scheme for wireless ATM has
`been discussed in [43].
`
`B. Design of Link Layer
`
`The data link layer in WIATM contains the wireless ATM
`(W-ATM) layer, wireless ATM adaptation layer (W-AAL), and
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`Fig. 5. Cell flow in the WIATM network.
`
`wireless data link layer (W-DL). The ATM and AAL design
`labels the cell relay paradigms of the ATM network for the
`transport of broad-band integrated traffic. The ATM and AAL
`protocols in the ATM network are designed based on a high-
`speed reliable point-to-point link. Hence, evaluations of the
`ATM and AAL protocols for wireless ATM are necessary.
`Reference [1] proposes new AAL’s to increase the trunking ef-
`ficiency by multiplexing variable air interface packets (AIP’s).
`The proposed AAL protocol by [1] has been standardized as
`a new AAL-2 protocol [44], [45]. The flexible radio interface
`design of [3] intends to replace the overhead of the ATM
`cell with wireless payload overhead and to segment the cell
`to fit in the CDMA frame structure. The radio interface can
`also carry the small IS-95 CDMA voice frame. Both of the
`frame structures are converted to the standard ATM cell with
`5 byte overhead in the base stations and are sent through
`the access network. The data link layer protocol design by
`[8] defines a PCN data link packet as a 53 byte ATM cell
`encapsulated by an additional PCN header. Reference [10] has
`an additional mobile logical link control (M-LLC) sublayer,
`which composes selective repeat ARQ to reduce the cell loss
`ratio.
`1) Design of Wireless ATM Layer: Our approach in the
`wireless ATM (W-ATM) layer protocol design is toward
`improving the reliability of the wireless connectivity instead
`of accommodating the routing in the ATM layer protocol
`of the B-ISDN UNI specified in [31]. The 5 byte ATM
`header consists of 3 byte virtual connection information (VCI
`and VPI, and 4 bit flow control information in UNI) for
`routing in the ATM network. The VCI/VPI setup in the
`ATM network requires full capability of the SS7 signaling
`network for number translation and contracting the transport
`bandwidth. The WIATM network architecture is designed as
`an independent wireless access network in Section III. The
`
`routing capability in WIATM is supported inside the wireless
`network only. The location management in WIATM is located
`at the radio port controller (RPC) of MSC. The RPC controls
`every radio with one-to-one correspondence in the BS. Each
`radio connects to one mobile user through the functionalities
`of the MAC protocol. The logical connection between the
`mobile user and the MSC is one-to-one correspondence.
`Therefore, the VCI/VPI information field is an overlapped
`routing information field. The W-ATM protocol excludes the
`VCI/VPI field. The cell flow is shown in Fig. 5.
`The cell loss priority (CLP) and payload indication (PI)
`in the ATM header are end-to-end indications for cell loss
`rate, network congestion status, and OAM message. These
`two functionalities are included in our W-ATM protocol and
`are also mentioned in [3]. The header error control (HEC)
`field in the ATM header is designed to protect the header
`information to avoid misdelivery in the ATM network. The
`W-ATM protocol design is to extend the 1 bit error-correcting
`capable HEC for header to multiple error correcting for the
`whole cell, as mentioned in Section III-B. The design of
`the W-ATM protocol selects BCH forward error correction
`(FEC) block coding. An example of the performance analyzes
`needed is to determine the length of the BCH coding which,
`bursty error-correcting capability, is required to
`in terms of
`BER performance for low-resolution
`reach the minimal 10
`video service [11]. As mentioned in Section III-B, the BER
`in the W-PL proto-
`performance is controlled below 10
`col design. Fig. 6 shows the cell error rate (CER) at the
`W-ATM layer versus the BER performance of the W-PL with
`-error-correcting capability BCH code.
`is shown in
`and
`The error-correcting capability
`is total block
`where
`Fig. 6. The BCH codeword set
`is the block length of the information field, and
`is
`length,
`the minimum distance of the codeword, determines the error-
`
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`CHENG AND HOLTZMAN: WIATM NETWORK AND PROTOCOL DESIGN
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`
`Fig. 6. Reliability control using FEC in the W-ATM layer protocol.
`
`correcting capability. In the WIATM network, the block length
`of the information field
`is fixed and is equal to 384 bits (48
`byte payload) plus 4 bit CLP and PI. Therefore, the minimal
`set of the total