An architecture of ATM-based PCS network: Signaling ... - CiteSeerX

Telecommunication Systems 14 (2000) 75–93

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An architecture of ATM-based PCS network: Signaling traffic and capacity ∗ Duk Kyung Kim a , Seung Joon Lee b , Dae Woo Choi c and Dan Keun Sung a a

Department of EE, KAIST, 373-1 Kusong-Dong, Yusong-Gu, Taejon 305-701, Korea E-mail: [email protected], [email protected] b Hyundai Electronics Industries Co., Ichon-Si, Kyoungki-Do 467-701, Korea E-mail: [email protected] c ETRI, 161 Kajong-Dong, Yusong-Gu, Taejon 305-350, Korea E-mail: [email protected]

In this paper, we propose an ATM-based Personal Communication Service (PCS) network architecture with ring-based access networks. We also propose a simple ring management scheme using ATM Add-Drop-Multiplexers (ADM). The ring has a Virtual Star topology, and we manage its bandwidth at two levels: Virtual Path (VP) level and Virtual Channel (VC) level. We consider four different types of configurations according to the locations of visitor location register (VLR) and mobile switching center (MSC) functions, and obtain signaling load and processing load. A 150 Mb/s-dual ring can support about 5,500 homogeneous ON– OFF voice sources. This ring capacity corresponds to covering approximately 180 cells in the case of 30 connections per cell. Even though we are here concerned with evaluating the proposed network for voice traffic, we can extend this study to the analysis of the proposed ATM-based PCS network accommodating various types of multimedia traffic as a further study.

1.

Introduction

In spite of the advances in mobile communication systems, most of the systems have utilized Public Switched Telephone Networks (PSTN) as their infrastructures. Current mobile network infrastructures may not be suitable in the near future because they utilize low-rate links and allocate mobile-related functions in mobile switching center (MSC). Since Asynchronous Transfer Mode (ATM) is the most promising technique in wired networks to implement Broadband-Integrated Services Digital Network (B-ISDN) supporting all types of traffic in a common backbone network, we expect mobile communication systems are to be integrated with B-ISDN. Integration of mobile communication systems with B-ISDN has the following advantages [2,4,8,12,13]: Common use of infrastructures, common use of functions and protocol parts, and common services. Since PCS and ATM networks are of increasing interest and are expected to be early implemented in Korea, the integration of PCS and ATM networks ∗

This study was supported in part by the Samsung Advanced Institute of Technology.

 J.C. Baltzer AG, Science Publishers

76

D.K. Kim et al. / An architecture of ATM-based PCS network

(ATM-based PCS networks) will be essential and thus the architecture and performance analysis of ATM-based PCS networks should be provided. Since voice and low-rate data are the main PCS services at present and will be expected to be continued in the near future, the performance and architecture of ATM-based PCS networks may largely depend on voice traffic for the present. STAR-based architectures [14,15] and Metropolitan Area Network (MAN)-based architectures [5,9,10] have been proposed for the integrated networks. MAN-based architectures achieve distributed control by distributing their functional entities such as basestations, databases, gateways, and mobile control units over MAN nodes. Slot generation/stop processings and signaling of speech/silence information are introduced to support ON–OFF voice traffic efficiently [9,10]. However, these architectures have two drawbacks: First, they require additional nodes, protocols, and overhead processings for the communications among distributed functional entities. Second, the Distributed Queue Dual Bus (DQDB) protocol and slot generation/stop processings incur considerable processing load. We propose an ATM-based PCS network architecture with ring-based access networks. Utilizing ATM Add Drop Multiplexers (ADM), we can simply manage a ring at Virtual Path (VP) and Virtual Channel (VC) levels. We classify the proposed architecture into four types of configurations according to the location of visitor location register (VLR) and mobile switching center (MSC) functions. We compare signaling load on various links as well as processing load at various nodes and investigate the effects of the location of functional entities. We also calculate ring capacity in terms of the maximum carried traffic load in a homogeneous ON–OFF voice traffic environment. Section 2 describes an ATM-based PCS network architecture and the functions of network entities. A simple ring management scheme in access networks is also suggested in this section. Section 3 presents signaling procedures of originating calls, terminating calls, handoff calls, and location updates. Section 4 compares four types of configurations in terms of the signaling load and the processing load. Section 5 calculates ring capacity. Finally, section 6 gives conclusions and further works. 2.

ATM-based PCS network

We propose an ATM-based PCS network architecture with ring-based access networks. We describe the architecture and the functions of network entities in detail. We also suggest a simple ring management scheme for the access networks of the proposed architecture. 2.1. Architecture Figure 1 shows a proposed ATM-based PCS network architecture. It consists of access networks and a backbone network. In the access networks, multiple rings can be connected to a backbone network, and they are controlled by an access switch (AS). Several ring nodes (RNs) are located in a ring, and base station controllers (BSCs) can


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Figure 1. A proposed ATM-based PCS network architecture.

be connected to RNs. As an alternative configuration, several RN/BSCs are located in a ring. Several base transceiver stations (BTSs) may be managed by either a RN/BSC or a BSC. A backbone network consists of a transport network and an intelligent network. Through the intelligent network, databases such as VLR, home location register (HLR), and authentication center (AUC) may be accessed for mobile-related functions. VLR may be located at AS for direct access without utilizing the backbone networks. Mobile environments are very different from fixed network environments. ATMbased networks ensure reliable transmission through end-to-end connections with broadband bandwidth. On the other hand, wireless links are prone to error and usually have narrow bandwidth. We assume the interface between ATM and wireless protocol is located at BSC. The BSC should be designed by considering simple interfaces with ATM networks as well as mobile environments. In addition to the protocol conversion between ATM and wireless networks, the BSC performs intra-BSC handoffs and radio resource management. The RN may manage single or several BSCs. MSC functions may be located at AS or Local Exchange (LEX). The MSC functions include mobile call processing, interface with VLR, and most of the mobilerelated functions such as handoff (except intra-BSC handoff), paging, synchronization, location registration/update, authentication, and encryption. VLR is related to the mobile functions such as location update, originating/terminating call processing, and handoff processing. The location of these functional entities largely affects network performance, which will be analyzed in section 4. The BTS performs wireless interface,

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Figure 2. Virtual Star topology for ring management.

and the RN does ring access using ATM ADM [21] and bandwidth management within RN. 2.2. Ring management scheme Utilizing broad transmission bandwidth of ATM-based rings, we adopt a Virtual Star topology in a ring, which has one-to-one virtual path between AS and RN as shown in figure 2. Thus, ring bandwidth is partitioned for each RN according to its traffic load. Specific VPI/VCI values may be allocated for signaling channels and a dual-ring structure may be employed for survivability. The ring control part located at AS manages ring bandwidth at VP level, and there is no special control to support ON–OFF voice traffic as described in MAN-based architectures. Since mobile traffic is statistically multiplexed in an RN, only partitioning effect may cause a slight decrease in bandwidth efficiency. In addition to the VP level management by AS, the VC level management by RN enables us to manage ring bandwidth hierarchically. Since this ring management can be done by utilizing ATM ADM functions, there is no need for the complex protocol conversion like MAN–ATM, and thus we can simply interwork with ATM/B-ISDN. 2.3. Characteristics of the proposed architecture We now describe the characteristics of the proposed architecture in detail.


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• Ring-based access network. Since the 155 Mb/s or n×155 Mb/s ring-based access network can be shared by the mobile users within its coverage area, its bandwidth can be efficiently utilized. • VP-based ring management. Since hundreds of mobile users may communicate through an RN in this architecture, the mobile user traffic is aggregated in an RN. Thus, even if a single traffic source is rather bursty, the aggregate traffic may be smoothed due to statistical multiplexing effect. Hence, utilizing VP through an RN, we can simply manage a ring and reduce processing load at ring control part without significant degradation in bandwidth efficiency. • Hierarchical bandwidth management. Ring control part manages the VP bandwidth assigned to each RN [19]. And each RN manages the VC bandwidth allocated to mobile users. Thus ring bandwidth can be hierarchically managed in access networks. • Simple control. In order to support ON–OFF voice traffic efficiently, a MAN-based architecture stops slot generations at any transitions from ON state to OFF state and resumes at any reverse transitions [9]. This control may be suitable for the wireless links where a small number of terminals communicate through a BS. But it may cause a large amount of processing load and signaling load to control a whole ring together with DQDB protocol. In the proposed architecture, the traffic from hundreds of mobile users may be aggregated and statistically multiplexed in an RN without such a complex control. • Simple interworking with ATM/B-ISDN. Since the proposed architecture utilizes ATM Add Drop Multiplexers (ADM), we can simply interwork with ATM/B-ISDN without any complex protocol conversion like MAN–ATM. 2.4. Comparison with the previous architectures The direct and exact comparisons of the proposed architecture with other ones are difficult due to the factors such as different protocols, different signaling procedures, different functional entities (FEs), and the physical mapping of the FEs. We here compare the proposed architecture with STAR- and MAN-based ones. Compared with a STAR-based architecture, the preposed architecture is more bandwidth efficient. For example, we assume that 10 RNs are connected to an AS, and the required number of connections by each RN varies from 100 to 500 according to its traffic load, but the aggregated traffic load at an AS requires 3,000 connections. In this situation, the link to each RN should have a bandwidth of 500×(bandwidth of a connection) and 10 such links are required in the STAR-based architecture. In the proposed architecture, RNs share a ring with about 60% bandwidth of that in the STAR-based architecture. The change of the VP bandwidth allocated to each RN can be performed easily through Network Management Center (NMC) because it does not require complicated controls in physical equipment [17]. For the statistical multiplexing of ON–OFF traffic, the MAN-based architecture requires (the number of ON–OFF

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transitions/s) × (the number of connections in a MAN) processings. Moreover, it needs the additional nodes such as bandwidth manager (BWM), signaling termination (ST), and head of bus (HOB), and also requires the communication among these MAN nodes [9,10]. If the MAN utilize the DQDB protocol, it should provide an MAN–ATM/BISDN conversion to access the ATM backbone network in addition to a wireless–MAN conversion. 3.

Signaling procedures

We describe the signaling procedures among the functional entities such as BSC, VLR, MSC, and HLR. The proposed architecture has four different configurations according to the locations of VLR and MSC functions as illustrated in figure 3. Since the proposed architecture is based on ATM/B-ISDN, we utilize B-ISDN signaling procedures (e.g., Q.2931 and B-ISUP) for call processing. There are no signaling procedures in B-ISDN for authentication, location update, paging, and handoff call. Thus, GSM and FPLMTS are referred for these cases [3,11]. Location updates may be classified into intra-VLR and inter-VLR cases, and handoff may be divided into three types: intra-BSC, intra-MSC, and inter-MSC.

Figure 3. Four types of configurations.


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3.1. Location update When a mobile terminal changes its location area, it requests a location update. If a location update is requested within the same VLR, the location information of the VLR is updated. Otherwise, the following processings are taken: (1) HLR information is updated. (2) User’s service profile is downloaded from the HLR to a new VLR. (3) User’s information is deleted in an old VLR. Figure 4 describes a procedure for inter-VLR location updates, where International Mobile Terminal Identity (IMTI) is a permanent address of terminal and New Temporary Mobile Terminal Identity (TMTI) value is assigned at each location update.

3.2. Originating call Figure 5 shows an originating call signaling procedure. When a mobile terminal requests a call, MSC checks whether it can accept the call. If the call is accepted, both wired and wireless channels are set up in access networks after authentication.

Figure 4. Inter-VLR location update signaling procedure.

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Figure 5. Originating call signaling procedure.

Receiving the routing information of a called user from the corresponding HLR, MSC establishes a channel to the called user and connects the call to both users. 3.3. Terminating call Figure 6 illustrates a terminating call signaling procedure. When an IAM message arrives at a terminating MSC, the MSC pages the called user after referring to VLR. Then the MSC establishes wired and wireless channels and connects the call.


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Figure 6. Terminating call signaling procedure.

3.4. Handoff In mobile-controlled or mobile-initiated handoff mechanisms, a mobile terminal requests a handoff to a new BSC and then the BSC checks the type of handoff. IntraBSC handoff calls are handled by BSC, while the other types of handoff calls are done by MSC. Intra-MSC and inter-MSC handoffs are processed by their own procedures. Figure 7 illustrates an intra-MSC handoff signaling procedure.

4.

Signaling traffic analysis

We now calculate signaling traffic load and compare the previously described four types of configurations in the proposed architecture. Since signaling messages require transmission bandwidth on a link as well as some processings at related nodes, we calculate both the signaling load on various links and the processing load at various nodes, which are represented by the number of signaling cells transmitted on a link in an hour and the number of signaling messages processed at a node in an hour, respectively. Signaling traffic load here means both signaling load and processing load,

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Figure 7. Intra-MSC handoff signaling procedure.

and we assume that a single signaling message is delivered using a single signaling ATM cell. We first calculate the signaling traffic load originated by each call processing signaling procedure. This can be done arithmetically by using the signaling procedures described in the previous section. Then we compute the frequency of call processings assuming square shaped cells and location areas. We adopt the terminal mobility model in [7], where the users with constant speeds change their directions in four directions, right, left, back, or straight at memoryless points. An LEX area is shown as an example of a network configuration in figure 8 with the following variables: • • • • •

2 : NSD 2 : NDR 2 : NRN 2 : NNB 2 : NBC

number of ASs per ATM LEX, number of rings per AS, number of RNs per ring, number of BSCs per RN, number of cells per BSC.

We assume that a location area (LA) is identical to a ring area and a VLR manages several LAs. The frequency of intra-VLR location updates, Nloc1 , between two neighboring LAs belonging to a same VLR and the frequency of inter-VLR location updates, Nloc2 ,


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Figure 8. An example of a network configuration (single LEX area).

between two neighboring VLR areas are calculated as  number of terminals 2   NBC NNB NRN d E[V ]NDR (NDR − 1)NSD  2  km    for configurations 1 and 3, (1) Nloc1 = number of terminals    NBC NNB NRN d E[V ]NDR NSD (NDR NSD − 1)   km2   for configurations 2 and 4,  number of terminals 2   NBC NNB NRN d E[V ]NDR NSD  2  km    for configurations 1 and 3, Nloc2 = (2)  number of terminals   N N N d E[V ]N N BC NB RN DR SD   km2   for configurations 2 and 4, where d and E[V ] are one side length of cell and mean terminal speed, respectively. Since call arrival rate in unit area, Ncall , is given by 1 Erlang number of terminals Ncall = , (3) 2 terminal E[T ] km

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the frequencies of originating calls, Norig , and terminating calls, Nterm , are expressed as Norig = Ncall (LEX area) Pr{MS originating}, Nterm = Ncall (LEX area) Pr{MS terminating},

(4) (5)

where LEX area is the area managed by a LEX, and Pr{MS originating} and Pr{MS terminating} denote the probabilities of originating and terminating calls, respectively. The frequencies of intra-BSC handoffs, Nho1 , intra-MSC handoffs, Nho2 , and interMSC handoffs, Nho3 , are derived as 2 2 2 2 NDR NRN NNB NBC (NBC − 1), Nho1 = Nh NSD  2 Nh NSD NDR NRN NNB (NDR NRN NNB − 1)NBC     for configurations 1 and 2, Nho2 =  Nh NSD NDR NRN NNB (NSD NDR NRN NNB − 1)NBC    for configurations 3 and 4, 2 N N N N Nh NSD DR RN NB BC for configurations 1 and 2, Nho3 = Nh NSD NDR NRN NNB NBC for configurations 3 and 4,

(6)

(7)

(8)

where the frequency of handoffs per cell is given by Nh = Ncall (cell area)

E[V ]E[T ] . d

(9)

Here E[T ] is the mean call holding time. Using the above results, we can obtain the signaling traffic load in a given network environment. Table 1 shows the signaling load on a link between AS and LEX (an AS–LEX link) and the processing load at various nodes in the case of type 1 configuration. We assume the PCS environments and network parameters shown in table 2 and calculate the signaling load and processing load of four types of configurations. Figure 9 shows the processing load at various nodes and the signaling load on an AS–LEX link for four configurations. The processing load is the heaviest at LEX among all configurations. The location of VLR affects its coverage area and the frequency of intra/inter-VLR location updates. And the location of MSC also affects its coverage area and the frequency of intra/inter-MSC handoffs. In addition, since network entities process a different number of signaling messages according to the locations of VLR and MSC, their locations largely affect signaling traffic load. Figure 10 compares the signaling load on an AS–LEX link and the processing loads at various nodes in detail. The location change of MSC functions from AS to LEX increases the frequency of intra-BSC handoffs, but slightly decreases the frequency of inter-MSC handoffs. The amount of change, however, is small and the processing load at RN is nearly identical for each configuration (see figure 10(a)).


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Table 1 Signaling traffic load in the case of type 1 configuration: (a) processing load at various nodes; (b) signaling load on an AS–LEX link. (a)

Intra-VLR LU Inter-VLR LU Orig. call

RN

AS

LEX

VLR

0 0 Norig 2 2 2 2 NSD NDR NRN

2 4Nloc1 /NSD 2 4Nloc2 /NSD

0 0

2 2Nloc1 /NSD 2 5Nloc2 /NSD

2 8Norig /NSD

4Norig

2 Norig /NSD

Term. call

2

Nterm 2 2 2 NSD NDR NRN

2 8Nterm /NSD

4Nterm

2 Nterm /NSD

Call release

2

Norig + Nterm 2 2 2 NSD NDR NRN

2 3(Norig + Nterm )/NSD

2(Norig + Nterm )

0

Intra-BSC h/o

4

Nho1 2 N2 N2 NSD DR RN

0

0

0

Inter-BSC h/o

5

Nho2 2 2 2 NSD NDR NRN

2 4Nho2 /NSD

0

0

Inter-MSC h/o

7

Nho3 2 2 2 NSD NDR NRN

2 9 Nho3 /NSD

0

2 Nho3 /NSD

(b) Links Intra-VLR loc. update Inter-VLR loc. update Originating call Termination call Call release Intra-BSC handoff Inter-BSC handoff Inter-MSC handoff

AS−LEX 0 2 6Nloc2 /NSD 2 6Norig /NSD 2 4Nterm /NSD 2 2(Norig + Nterm )/NSD 0 0 2 12 Nho3 /NSD

Table 2 PCS environments and network parameters. Traffic per terminal (Erlang/terminal) Terminal density (number of terminals/km2 ) d E(T ) E(V ) Pr{PS originating} 2 NSD 2 NDR 2 NRN 2 NNB 2 NBC

0.1 E 15,000 0.126 km 100/3600 h 1 km/h 0.5 16 4 16 1 9

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Figure 9. Comparison of signaling traffic load.

Irrespective of the location of MSC functions, both AS and LEX process the messages related to channel setups and releases. However, the location change of MSC functions from AS to LEX reduces the processing load at AS by about 70% and increases the processing load at LEX by about 100% (see figures 10(b) and (c)). The location change of VLR from AS to LEX increases the coverage area of VLR and the frequency of intra-VLR location updates, but decreases the frequency of inter-VLR location updates. In addition, since the number of signaling messages for intra-VLR location updates is less than that for inter-VLR location updates, the processing loads at VLR in configurations 2 and 4 increase about 13 times compared with those in configurations 1 and 3 (see figure 10(d)). When MSC functions are located at AS, the total processing load increases by about 7% compared with that in the case LEX performs MSC functions. The total processing load becomes 1–2% smaller by the location change of VLR from AS to LEX as shown in figure 10(e). Signaling load on an AS–LEX link largely varies according to the location of VLR and MSC (see figure 10(f)). The signaling load is the smallest in configuration 1, where both MSC and VLR are located at AS. On the other hand, configuration 3 has the largest signaling load because BSC, MSC, and VLR utilize an AS–LEX link to exchange signaling messages one another.


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Figure 10. Detailed comparisons of processing load at various nodes, comparison of signaling load on an AS–LEX link, and total processing load (the unit of y-axis: messages/s).

From the above results, configuration 1 has the largest processing load. However, it distributes processing load and has the smallest signaling load on an AS–LEX link. When the processing capability of VLR is large, configuration 2 can be adopted without significant effects on the other nodes and links. Although the smallest processing load is achieved by configuration 4, the major processing load is concentrated at LEX, and the signaling load on an AS–LEX link is increased. Configuration 3 has the largest signaling load on an AS–LEX link and requires large processing capability of LEX.

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5.


Ring capacity

We now calculate ring capacity in terms of the maximum carried traffic load in a single ring. Since the ring bandwidth is partitioned for each RN in the proposed architecture, we can focus on a specific RN. Since the RN performs multiplexing function, we can model it as a G/D/1 queue with constant service time 1/µ and buffer size K for upstream traffic. The mobile call arrivals to an RN are assumed to be a Poisson process. Service rate and buffer size are closely related to the allocated bandwidth and QoS requirements. For statistical multiplexing, the performance can be characterized by two types of measures: cell performance and connection performance. The cell performance is expressed in terms of delay and cell loss probability. The connection performance is represented by the blocking probability of virtual connection establishment requests [16,17]. In this section, we calculate ring capacity in the case of a homogeneous ON–OFF voice traffic for simplicity. ON and OFF durations are exponentially distributed with means 350 ms and 650 ms, respectively, and the peak rate is 64 kb/s [1]. We assume that voice traffic requires the maximum delay of 10 ms, the cell loss probability of 10−3 , and the connection blocking probability of 1% in an RN [13]. To obtain the ring capacity satisfying all of the above requirements, we first determine the buffer size and bandwidth allocated to an RN, and then calculate maximum carried traffic load by considering the connection performance. Cell performance. We determine the values K and µ satisfying the cell performance for N multiplexed voice sources. µ is service rate in the unit of b/s and is equal to the bandwidth allocated to an RN. Given K and µ, the maximum delay can be calculated as 1 (10) Maximum delay = K 424, µ where ATM cell size is 424 bit. For N ON–OFF/D/1/K queueing system, we can obtain the value µ satisfying the cell loss probability of 10−3 from simulations. Connection performance. We consider a simple connection admission control (CAC) for a homogeneous voice traffic. When an RN can support N connections with bandwidth µ, a new connection is admitted when the following condition is satisfied. 1 + i 6 N,

(11)

where i is the number of ongoing connections. Assuming the connection blocking probability of 1%, we can calculate carried traffic load from the following recursive type Erlang-B formula EN (a) =

aEN −1 (a) , N + aEN −a (a)

(12)


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where aN /N ! EN (a) = PN k k=0 (a /k!)

and

E0 (a) = 1.

Using the above results, we can calculate the maximum carried traffic load ρring which can be accommodated in a 150 Mb/s-dual ring as follows: (1) Determine the maximum number of supportable connections by the ith RN, Ni (i ∈ {1, 2, . . . , M }) according to the given network topology and traffic load, where M RNs are assumed to be located in a ring. (2) Determine the queue size Ki and the service rate µi of the ith RN satisfying the cell performance by using simulations. (3) Calculate the carried traffic load by the ith RN, ai , satisfying the connection performance using (12). (4) Calculate ρring utilizing the equation ρring =

M X

ai ,

(13)

i=1

where the total allocated bandwidth, µT should not exceed the ring capacity. µT =

M X

µi 6 150 Mb/s.

(14)

i=1

In symmetrical loading of each RN, where N = Ni , µ = µi , and a = ai for all i, (13) can be simplified as 150 Mb/s a, (15) ρring = µ where bxc is the greatest integer value less than or equal to x. The first term in the right side of (15) denotes the maximum number of RNs in a ring, where µ b/s is the allocated VP bandwidth of each RN. Figure 11 shows ρring when voice activity is 1 and 0.35 under the symmetrical RN loading. When N is 300 and voice activity is 0.35, ρring is about 5,500. In the case of 30 connections per cell, a ring can accommodate approximately 180 cells. Since signaling traffic is very small compared with ring bandwidth, we here exclude this traffic in calculating ring capacity. We obtain µT and ρring for three more cases as in table 3, by varying the number of RNs with N = 100, 300, and 500. We note that the number of RNs in a ring largely affects ρring due to a partitioning effect, but the asymmetrical loading makes a little changes in ρring for the same number of RNs in a ring.

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Figure 11. Ring capacity. Table 3 Comparison of µT and ρring for various values of the number of RNs with N = 100, 300, and 500. Case I: 20RN(300), case II: 10RN(500) + 10RN(100), case III: 6RN(500) + 27RN(100), and case IV: 12RN(500), where RN(i) denotes the RN with N = i.

µT (Mb/s) ρring

6.

Case I

Case II

Case III

Case IV

149.8 5538

149.8 5580

149.1 5112

146.1 5688

Conclusions

We proposed an ATM-based PCS network architecture with ring-based access networks. Ring bandwidth is partitioned for each RN, and each partitioned bandwidth has its own VP. Mobile user traffic can be aggregated and statistically multiplexed in an RN. Ring bandwidth can be managed at VP and VC levels by AS and RN, respectively. We utilize ATM ADMs in order to have a simple ring control and to reduce the processing complexity. Compared with MAN-based architectures, the proposed network has no complicated protocol such as DQDB and slot generation/stop processings. According to signaling procedures, we calculated the frequencies of originating calls, terminating calls, handoffs, and location updates. We compared the signaling load and processing load of four different configurations and investigated the effect of the location of VLR and MSC functions. These results can be useful in designing ATM-based PCS networks under the given conditions such as subscriber environment and the capability of network entities. A dual ring with transmission bandwidth of 150 Mb/s can support about 5,500 ON–OFF voice sources under symmetrical RN loading in the case that N is equal to 300. This ring capacity corresponds to covering approximately 180 cells if we assume 30 connections per cell. As a further study, we can extend this study to the analysis of the proposed ATMbased PCS network accommodating broadband/multimedia traffic as well as voice


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traffic. Signaling messages/procedures may be modified and novel traffic managements such as priority control and VP/VC management are needed to support the future multimedia traffic with various bandwidths and multiple QoS requirements. References [1] H. Akimaru and K. Kawashima, Teletraffic: Theory and Applications (Springer, Berlin, 1993). [2] E. Buitenwerf, G. Colombo, H. Mitts and P. Wright, UMTS: Fixed network issues and design options, IEEE Personal Communication Magazine 1 (1995) 30–37. [3] CCIR FPLMTS recommendations 687-1. [4] J.S. Dasilva and B.E. Fernandes, The European research program for advanced mobile systems, IEEE Personal Communication Magazine 1 (1995) 14–19. [5] D.J. Goodman, G.P. Pollini and K.S. Meier-Hellstern, Network control for wireless communications, IEEE Communication Magazine 12 (1992) 116–124. [6] D.K. Kim, S.J. Lee, D.W. Choi and D.K. Sung, An architecture of broadband personal communication networks, in: PIMRC-96 (1996) pp. 603–607. [7] T.S. Kim and D.K. Sung, The effects of handoffs on microcell-based PCN networks, in: GLOBECOM-94 (1994) pp. 1316–1320. [8] J.A. Korinthios, H. Mitts and E.D. Sykas, Scenarios for integration of universal mobile telecommunication system (UMTS) into broadband ISDN, in: VTC-94 (1994) pp. 1596–1600. [9] V.C.M. Leung, N. Qian, A.D. Malyan and R.W. Donaldson, Call control and traffic transport for connection-oriented high speed wireless personal communications over metropolitan area networks, IEEE Journal on Selected Areas in Communications 12 (1994) 1376–1388. [10] A.D. Malyan, L.J. Ng, V.C.M. Leung and R.W. Donaldson, Network architecture and signaling for wireless personal communications, IEEE Journal on Selected Areas in Communications 11 (1993) 830–841. [11] M. Mouly, The GSM System for Mobile Communications (Marie-Bernadette PAUTET, 1992). [12] T. Norp and A.J.M. Roovers, UMTS integrated with B-ISDN, IEEE Communication Magazine 11 (1994) 60–65. [13] J. Rapeli, UMTS: Targets, system concept, and standardization in a global framework, IEEE Personal Communication Magazine 1 (1995) 20–28. [14] D. Raychaudhuri, ATM-based transport architecture for multiservices wireless personal communication networks, in: ICC-94 (1994) pp. 559–565. [15] D. Raychaudhuri and N.D. Wilson, ATM-based transport architecture for multiservices wireless personal communication networks, IEEE Journal on Selected Areas in Communications 12 (1992) 1401–1414. [16] K.W. Ross, Multiservice Loss Models for Broadband Telecommunication Networks (Springer, Berlin, 1995). [17] H. Saito, Teletraffic Technologies in ATM Networks (Artech House, 1994). [18] H. Saito, K. Kawashima and K. Sato, Traffic control technologies in ATM networks, IEICE Transactions on Communications E-74 (1991) 761–771. [19] Y. Sato and K.-I. Sato, Virtual path and link capacity design for ATM networks, IEEE Journal on Selected Areas in Communications 9 (1991) 104–111. [20] F. Vakil, A capacity allocation rule for ATM networks, in: GLOBECOM-93 (1993) pp. 406–416. [21] T.-H. Wu, D.T. Kong and R.C. Lau, An economic feasibility study for a broadband Virtual Path SONET/ATM self healing ring architecture, IEEE Journal on Selected Areas in Communications 10 (1992) 1459–1472.