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Cellular Networks Positioning Performance Analysis Reliability Part 9

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Tham khảo tài liệu 'cellular networks positioning performance analysis reliability part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Channel Assignment in Multihop Cellular Networks 229 use 10 10 for both uplink and downlink channel combinations the system capacity is 1.53 Erlangs which is limited by the downlink capacity as shown in Figure 11. Nevertheless if we use 46 4 instead of 10 10 for both uplink and downlink channel combinations the system capacity is 1.36 Erlangs which is limited by the uplink capacity. From Table 2 it can be seen that the maximum capacity supported by symmetric FCA is about 6.92 Erlangs with 28 7 for both uplink and downlink channel combinations. Therefore we need to make use of the AFCA in which the channel combinations N0 N1 for uplink and downlink are different in order to achieve larger system capacity. From Table 2 we suggest that with channel combination of UL 22 8 and DL 34 6 for downlink the maximum system capacity can be obtained to be as large as 9.31 Erlangs. Beyond the optimum combination if we further reduce N1 and increase N0 the performance will be degraded because more calls will be blocked in the virtual microcells. Combinations No N1 Uplink Capacity Erlangs Downlink Capacity Erlangs 10 10 4.43 1.53 16 9 8.51 3.33 22 8 9.31 5.55 28 7 6.92 7.89 34 6 4.88 10.46 40 5 2.92 12.92 46 4 1.36 14.21 52 3 0.33 9.08 Table 2. System capacity for uplink and downlink vs. channel combinations. 4. Proposed dynamic channel assignment scheme Abovementioned results show that CMCN with AFCA can improve the system capacity. However FCA is not able to cope with temporal changes in the traffic patterns and thus may result in deficiency. Moreover it is not easy to obtain the optimum channel combination under the proposed AFCA which is used to achieve the maximum system capacity. Therefore dynamic channel assignment DCA is more desirable. We proposed a multihop dynamic channel assignment MDCA scheme that works by assigning channels based on the interference information in the surrounding cells Chong Leung 2001 . 4.1 Multihop dynamic channel assignment Figure 13 also shows the