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services to cells 1–4, and R3 to cells 5–7. 10 Initially, when the mobile station (MS) is in cell 1, it reserves resources along the path shown by the thick lines from base station 1 to R2 to R1. If the MS now moves into cell 2, it is attached to base station 2 and makes a reser- vation along the new route from base station 2 to R2. In RSVP, because a receiving host cannot initiate a reservation request (using the RESV message) until it has received a PATH message and because a data source sends the PATH message periodically, the MS must wait before it can make the new reservation. Mean- while, R2 continues to send packets along the old route to cell 1, Chapter 9 326 MS Handover PSPDN R1 R2 R3 1 2 3 4 5 PATH RESV 6 7 Figure 9-18 RSVP in a mobile environment 10 Notice that router R1 is functionally equivalent to a Gateway GPRS Support Node (GGSN) of a GPRS or all-IP wireless network. Similarly, routers R2 and R3 corre- spond to Serving GPRS Support Nodes (SGSN). and so these packets are lost by the MS. This problem may be some- what mitigated by modifying RSVP so that as soon as the MS is handed over to the new cell, R2 issues a PATH message. However, since the resource reservation process is rather slow, the associated delays may still be too long to avoid any packet loss. The problem becomes particularly severe if the MS moves into a cell where the traffic is already quite high. In this case, the MS must renegotiate with the network for the allocation of required resources, leading to even longer delays and further loss of packets. And depending upon the requested QoS, the network may not be able to guarantee the desired quality, and consequently, may even deny the reservation request. This problem can be solved if the network has some prior knowl- edge of how a mobile station is going to move around in a serving area. Reference [12] suggests an extension of RSVP, called Mobile RSVP (MRSVP), based upon this idea. In this protocol, the network maintains in its database a list of all nodes that are likely to be vis- ited by an MS. The MS reserves resources at all of these nodes in advance, even though it will be using resources at only one of them at any time. In this way, delays caused by the negotiation and reser- vation of resources can be eliminated. The flow of RSVP messages in this protocol is shown in Figure 9-19. Because the MS may visit neighboring cells 1, 2, and 3, resources are reserved along three dif- ferent routes. If the MS is located in cell 2, only the route, shown by the heavy lines, from the MS to base station 2 to R2 through R1 to the PSPDN is active, while the other two routes are passive. Although this protocol is conceptually simple, there are several dis- advantages: ■ Although only one of the routes is active at any time, the system must reserve resources at many other nodes. Much of these resources may never be used by this MS, but could have been used by other mobile stations for a more efficient utilization of the bandwidth. ■ An incoming call is blocked if requested resources are not avail- able at all nodes. Therefore, the call-blocking probability in- creases with the number of cells where the reservation is to be made. 327 Quality of Service (QoS) in 3G Systems ■ In many instances, an MS may not know in advance exactly how it is going to roam. As such, this protocol is not very practical. ■ If the number of cells that a mobile station may likely visit is large and if there are many mobiles in a serving area, the database that must be maintained by the network also becomes very large. Reference [13] has suggested another protocol called Mobile IP with Location Register (MIP-LR) for mobile wireless networks. According to this protocol, when a mobile station moves into a for- eign serving area, its new location is saved in the HLR. Subse- quently, when a source node has a packet to send to this MS, it receives the location address of the mobile from the HLR, and sends the packet directly to that address. However, it is still necessary to Chapter 9 328 PSPDN R1 R2 R3 1 2 4 PATH RESV 3 MS Figure 9-19 Reservation in MRSVP proposal reserve resources along the new route, and packets may be lost as resources are being reserved. Summary In this chapter, we have discussed QoS issues and concepts and described how it can be provided in 3G UMTS networks. Providing the QoS usually consists of four steps: requesting resources from the network in accordance with a desired quality, admission control of the newly arrived user, resource reservation by the network, and policing the incoming packets to ensure that users are not violating their contract. In order to request the QoS, the user must know how to characterize its traffic. With this end in view, we have classified the traffic that is likely to originate in UMTS and described the traf- fic attributes that can be used to create a reasonable set of simple QoS profiles. The RSVP protocol, admission control procedures, and policing schemes have been presented in some detail. Although many of the ideas of the QoS that are applicable to fixed networks extend to mobile networks, standard RSVP is not quite suitable. Problems that arise when RSVP is used in a mobile network are dis- cussed. A number of protocols based on the modification and exten- sion of RSVP have been suggested. A brief description of some of these protocols is presented. References [1] R. Braden, et al., “Resource Reservation Protocol (RSVP) — Version 1 Functional Specification,” RFC 2205, September 1997. [2] J. Wroclawski, “The use of RSVP with IETF Integrated Ser- vices,” RFC 2210, September 1997. [3] R. Braden, et al., “Integrated Services in the Internet Archi- tecture: An Overview,” RFC 1633, June 1994. [4] Internet Protocol, RFC 791, September 1981. 329 Quality of Service (QoS) in 3G Systems [5] S. Deering, et al., “Internet Protocol, Version 6 (IPv6) Specifi- cation,” RFC 2460, December, 1998. [6] M.R. Karim, ATM Technology and Services Delivery. New Jer- sey: Prentice Hall, 2000, pp. 87–98. [7] D.C. Lee, Enhanced IP Services for Cisco Networks. Indiana: Cisco Press, 1999, pp. 115–177. [8] N. Yamanaka, Y. Sato, and K. Sato, “Performance Limitation of the Leaky Bucket Algorithm for ATM Networks,” IEEE Trans. Commun., Vol. 43, No. 8, August 1995, pp. 2298–2300. [9] 3G TS 22.105 Release 1999, Services and Service Capabili- ties. [10] 3GPP TS 23.107: QoS Concept and Architecture, Release 1999. [11] B. Moon and H. Aghvami, “RSVP Extensions for Real-Time Services in Wireless Mobile Networks,” IEEE Commun. Mag., Vol. 39, No.12, December 2001, pp. 52–59. [12] A.K. Talukdar, et al., “MRSVP: A Resource Reservation Pro- tocol for an Integrated Services Network with Mobile Hosts,” Dept. Comp. Sci. Tech. Rep. TR-337, Rutgers University. [13] R. Jain, et al., “Mobile IP with Location Registers (MIP-LR),” Internet Draft, draft-jain-miplr-01.txt, July 2001. [14] S. Blake, et al., “An Architecture for Differentiated Services,” RFC 2475, December 1998. [15] K. Nicholas, et al., “Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers,” RFC 2474, December 1998. [16] Y. Bernet et al., “A Framework for Integrated Services Oper- ation over Diffserv Networks,” RFC 2998, November 2000. See the following web site for RFCs: http://www.cis.ohio-state.edu/ Chapter 9 330 Network Planning and Design CHAPTER 10 10 Copyright 2002 M.R. Karim and Lucent Technologies. Click Here for Terms of Use. The objective of network planning and design is to provide wireless telephony services in a serving area in the most cost-effective man- ner. In the case of an existing system, the objective is to expand and augment its facilities so as to add new features and capabilities or increase its capacity in case the system has reached its coverage limit. The design usually involves determining the number of base stations and their locations that would provide the necessary cover- age in a serving area, meet the desired grade of service, and satisfy the required traffic growth so that the total startup cost is minimized and the rate of return maximized. Clearly, if the network is well planned, it would be able to meet the traffic growth within the limits of its design until a point is reached where it becomes necessary to add new cells, assign new frequencies to an existing cell, or supple- ment the old system with a new one in a manner that is consistent with the quality of service objectives. Because base stations are to be connected to a mobile switching office, the design also requires the capacity and type of the connecting links to be specified. Sometimes elements of the core network may not be able to support new ser- vices, such as high-speed multimedia applications or gateway access to a packet data network. In these cases, the network planner must consider upgrading the switching systems. The design process is roughly the following [5], [6]. Service providers who want to own and operate the network generate a set of system requirements concerning the type of the desired system (such as analog, Global System for Mobile Communications [GSM], Code Division Multiple Access [CDMA], and so on), the expected traf- fic, and the desired service quality. In general, received signal-to- interference ratios and bit error rates are used as the quality of service indicators. Based on the above requirements, an appropriate propagation model is used to calculate a link budget that indicates the maximum allowable path loss for a given transmitter power so that the received signal-to-interference ratio at any point in the des- ignated serving area is sufficient to ensure the desired quality. Maps and the terrain of the serving area are inspected, and assuming approximate locations of base stations, the signal distribution over that area is calculated. One of the design goals is to provide coverage on the entire serving area with a minimum number of base stations consistent with the requirement of the projected traffic growth. Currently, software tools Chapter 10 332 are available that take into consideration design requirements as well as terrain features of the serving area, and given any number of base stations and their locations, they can plot the signal distribution over that area. If the coverage or the number of base stations is not optimum, the user can alter their number and locations and run as many iterations as necessary until the design objective is satisfied. The design might make assumptions about the maximum available transmitter power, commercially available transmitters types, spe- cific antenna (such as omnidirectional or sectored), their heights, and so on. It may be reviewed by engineers in consultation with the cus- tomer, modified if necessary, and when it is complete, all system com- ponents may be installed. Because the system, when actually installed, may not be exactly the same as the design (for example, the actual base station locations or their antenna heights may be slightly different), it may be useful to verify the design by running some field tests. System requirements fall usually into the following categories: ■ The coverage area This generally involves areas to be served, e.g. counties comprised by the area. It may also be necessary to include information on such things as the terrain and clutter, e.g., the average height and density of buildings, streets, hills, forests, large water bodies if any, highways, population distribution, and so on. ■ System-related requirements They should specify the following: ■ The technology type, indicating, for example, whether it should be CDMA, GSM, Wideband CDMA (W-CDMA), Time Division Multiple Access (TDMA), cellular, and so on ■ The allocated bandwidth, e.g., the number of available channels and the number of channel sets (that is, the reuse factor) ■ The type of antennas to be used (for the link budget calculation) ■ Maximum cell size and so on ■ The cost objective ■ The traffic This should include the following: ■ The number of mobile stations to be served 333 Network Planning and Design ■ The amount of traffic, e.g., the offered load per mobile and the holding time ■ The geographical distribution of the traffic if it is not uniform over the whole serving area ■ Specification of the traffic types (such as constant bit rate, variable bit rate, delay-intolerant data, elastic data, and so on) and relevant traffic descriptors (e.g., the maximum tolerable delay during the busy-hour period) ■ The probability of calls being blocked or the grade of service ■ Ratio of the total daily traffic to the busy-hour traffic For satisfactory service, the system should be designed so that the mobile stations receive a sufficiently strong signal inside buildings or vehicles where the penetration loss may be significant, outside buildings where there is no such penetration loss, and on highways. The system may then be designed so as to optimize one of the fol- lowing parameters or any combination thereof: ■ The signal distribution as received by mobiles or base stations ■ The S/I ratio at base stations ■ The S/I ratio at mobiles or any combination of these parameters However, the usual practice is to design the system such that both forward and reverse links have a balanced signal distribution. Network Design Spectrum Requirements Once the system requirements are known, the first step is to ensure that the service provider has licensed sufficient spectrum for the expected amount of traffic and the call-blocking probability. The sys- tem must be designed so that it can carry the peak traffic, that is, the traffic during a busy-hour period. The traffic is determined by the call arrival rate and the holding time of each call. The unit of traffic is the Erlang, which is defined as the traffic that a circuit can carry Chapter 10 334 TEAMFLY Team-Fly ® if it is utilized 100 percent of the time during a busy hour. The hold- ing time varies from applications to applications, but for telephone- type conversations during a busy hour, it lies in the range of 60 to 80 seconds. The probability that a call is blocked depends on the num- ber of traffic channels (circuits) available and the total amount of traffic coming into the network (the offered load), and is given by the well-known Erlang B formulation. Call-blocking probabilities for various values of the offered load and circuits are available as tables and graphs, where it is assumed that calls arrive at the system ran- domly with a Poisson distribution and that blocked calls are cleared; that is, when a call is blocked, it is not reinitiated [8], [9]. The traffic capacity in Erlangs as a function of the number of circuits for a few values of the call-blocking probability is given in Figure 10-7 of Appendix A to this chapter. The determination of the bandwidth is best explained by an example. Consider the following. Example. Suppose that it is necessary to design a cellular system for 50,000 subscribers. On the average, each subscriber makes about two calls during a busy hour, and the average holding time of a call is two minutes. Let us assume that the serving area is to have about 14 3-sector cells and that the traffic is uniformly distributed over the entire serving area. 1 If the call-blocking probability is to be 1 percent, how much bandwidth is required to provide the service? Solution for Case 1. First, let us consider an analog system. The total traffic during the busy hour ϭ No. of Subscribers ϫ No. Calls/hour ϫ Holding Time in hours ϭ 50,000 ϫ 2 ϫ (2/60) ϭ 3,333.3 Erlangs. So the traffic per sector of a cell ϭ 3,333.3/(No. of Cells ϫ No. of Sectors) ϭ 3,333.3/(14 ϫ 3) ϭ 79.36 Erlangs. The number of channels or circuits per sector required to support this traffic for a call-blocking probability of 1 percent (from Figure 10- 7) ϭ 95. In other words, 95 ϫ 3 or 285 channels are needed per cell. 335 Network Planning and Design 1 A few comments are in order here. First of all, the traffic is rarely uniform over a serv- ing area. It generally depends on the population distribution and is much higher in urban and suburban areas, gradually decreasing toward outlying areas. Secondly, the number of cells is not known at the outset. In fact, given the requirements, our goal is to determine this number. [...]... have an all-IP architecture I Interoperability between 3G and 4G and between 2G and 4G As for the time frame of 4G services, analog systems were introduced in the United States and Europe in 1981 Within 10 years, around 1991, digital systems were deployed The 3G systems are targeted for introduction in 2001 and 2002 Thus, it is reasonable to Chapter 11 360 Table 1 1-1 Video Resolution Uncom- Com- (pels... Reduction of Fast Fading UHF Mobile Radio Systems.” IEEE Trans Veh Tech, Vol VT-20, No 4, November 1971, pp 81–92 [2] Y Okumura, E Ohmori, T Kawano, and K Fukuda, “Field Strength and Its Variability in VHF and UHF Land -Mobile Radio Service,” Rev Elec Communication Lab., Vol 16, pp 825–873, 1968 Network Planning and Design 353 [3] M Hata, “Empirical Formula for Propagation Loss in Land Mobile Radio Services,”... Mobile IP Multimedia 100 GPRS: up to 170 kb/s IS-95B: 64 - 115 kb/s SMS, Mobile IP 16 Voice 10 kb/s 1990 GSM, IS-136 to 9.6 kb/s SMS 2000 Year 2010 2020 shown in Table 1 1-1 , where, for comparison, ISDN and PSTN video phones have also been included Some of the 4G features are I Unrestricted, seamless roaming and global mobility not only for voice, but also for data services over regional and. .. process of manufacturing 3G wireless equipment so that service providers can begin to roll out 3G services to their customers in the near future NTT DoCoMo of Japan has been actively developing 3G technologies Lucent Technologies of the United States has developed base station equipment (such as 3G1 X and 3G3 X) that will provide 3G services for cdma2000, UMTS, and UWC-136, and is currently conducting... offsets for the I-channel and Q-channel pilot pseudonoise (PN) sequences that are used in synchronous CDMA systems (such as IS-95 and cdma2000) to spread the forward and reverse channel transmissions Recall that these PN sequences, which are maximal length shift register sequences with a period of 215 chips, are first offset in time (or phase) by an amount that is unique for each base station and then... deployment of 3G and 4G services There is, however, an economic perspective as well For example, nearly one hundred billion dollars were spent for 3G licenses in Western Europe In addition, a considerable amount of capital is needed for the 3G infrastructure Thus, to ensure a reasonable rate of return from this capital investment, it is necessary to generate sufficient customer demand for 3G services and continue... traffic in present day mobile telephony consists of voice However, the demand for mobile data has gone up steadily, spurred to a large Beyond 3G 357 extent by the availability of the Internet-based applications This is apparent from the fact that the data service capability of earlier Global Systems for Mobile Communications (GSMs) was limited to short messaging service and circuit-switched data at rates... wearable PCs with voice-activated, hands-free operation, or specially designed keyboards that can be strapped to a wrist, and small LCD displays with magnifying optics attached to, or reflected onto, the user’s glasses I QoS For efficient utilization of bandwidth, the network must implement a flexible resource management scheme to provide mobile stations with an end-to-end QoS across all-IP networks Users... Bell Atlantic, AT&T, and SBC NTT DoCoMo had targeted year 2001 for nationwide deployment of a commercial 3G system Service providers, equipment manufacturers, and research laboratories have already begun looking beyond 3G NTT DoCoMo is working on their vision of the fourth-generation (4G) system, and has started defining and developing 4G services and technologies [1] Many research and development projects... kb/s As the demand for data services began to grow, the European Telecommunications Standards Institute (ETSI) developed a standard for General Packet Radio Service (GPRS), which is now being deployed in many countries of the world to provide packet mode data services at 12—20 kb/s per slot The forecasted growth in the voice and data traffic in mobile communications is shown in Figure 1 1-1 .1 Although . 2298–2300. [9] 3G TS 22 .105 Release 1999, Services and Service Capabili- ties. [10] 3GPP TS 23 .107 : QoS Concept and Architecture, Release 1999. [11] B. Moon and H. Aghvami, “RSVP Extensions for Real-Time Services. suggested another protocol called Mobile IP with Location Register (MIP-LR) for mobile wireless networks. According to this protocol, when a mobile station moves into a for- eign serving area, its new. following web site for RFCs: http://www.cis.ohio-state.edu/ Chapter 9 330 Network Planning and Design CHAPTER 10 10 Copyright 2002 M.R. Karim and Lucent Technologies. Click Here for Terms of Use. The