 66666 bytes. The PDF of the Packet_Size becomes: (2.56) where is the probability that x>m. It can easily be calculated as: (2.57) Then it can be calculated as: Hn agm = (2.58) with the parameters above the average size: Hn = 480 bytes [2,20,21] indicates that ac- cording to the values for a and k in the Pareto distribution, the average packet size u is 480 bytes. Average requested file size is = 25 X 480 bytes 22 12 kbytes. The inter-arrival time is adjusted in order to get different average bit rates at the source level. Table 2.7 illustrates characteristics of connectionless information rates for WWW from [20]. System Analysis Fundamentals Table 2.7 Characteristics of Connection-Less Information Types [20] Packet based infor- Avg. no. of Avg. reading Avg. amount of Avg. inter-arrival Parameters mation rates, e.g. packet calls time between packets within a time between for packet size Internet services in a session packet calls (s) packet call pakets (s)' distribution WWW surfing k = 81.5 UDD 8 kbit/s (= 1.1 WWW surfing 0.125 k = 81.5 UDD 32 kbit/s (= 1.1 WWW surfing 0.0625 k = 81.5 UDD 64 kbit/s (= 1.1 WWW surfing 0.0277 k = 81.5 UDD 144 kbit/s (= 1.1 WWW surfing 0.0104 k = 81.5 UDD 384 kbit/s (= 1.1 WWW surfing 0.00195 k = 81.5 UDD 2048 kbit/s a = 1.1 CONCLUDING REMARKS This chapter summarizes the essential background to investigate the UTRA physical layer and its impact on its architecture. It has provided the reference models to represent the communication environments and the signal processing issues. It was not the aim of the author to cover the different topics in depth but to set them as review points for fur- ther study when required. References TG32 UMTS - Radio Requirements. High Level Requirements Relevant for the Definition of the UTRA Concept, v3.0.1, 1998- TS 101 111 (UMTS 21.01) Universal Mobile Telecommunication System (UMTS); Overall Requirements on the Radio Interface(s) of the UMTS. Draft New Recommendation ITU-R M.[FPLMTS.REVAL] Guidelines for Evaluation of Radio Transmission Technologies f