Mobile Cellular Systems - Alak Roy

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Types of Handoff • Hard handoff – Mobile user is passed between disjoint towers that assign different frequency or adapt different air-interface technology. – Communication channel is released first and the new channel is acquired later from the neighboring cell. – Service disruption, reduction in QoS – Used by systems which use TDMA and FDMA such as GSM and GPRS • Soft handoff – Mobile user communicates to two or more towers simultaneously and the signal is treated as a multipath signal – Can establish multiple connections with neighboring cells. – Used in CDMA systems, where the cells use same frequency band using diff code words. – Each MS maintains an active set of BSs, where BSs are added and removed based on 2 RSS thresholds. So addition or removal of a BS to the active set is called Soft handoff. – Used by IS-95 and WCDMA • Without handoff 34
• Horizontal handoff Types of Handoff – Mobile user is passed between towers of homogeneous networks – Example: handoff involving two GSM cells. • Vertical handoff – Handoff between towers of different types of networks. – Handoff in heterogeneous networks. More complex compared to Horizontal handoff. – Example: handoff from one GSM based cell to one WCDMA-based cell . 35
Page 1 and 2: SLIDE #2.1 Mobile Cellular Systems
Page 3 and 4: Cellular Implementations (Gs) • 1
Page 5 and 6: Cellular Implementations(Gs) • 4G
Page 7 and 8: Frequency Division Duplex (FDD) mob
Page 9 and 10: Number of User Channels in AMPS •
Page 11 and 12: Cellular Architecture MSC PSTN MS B
Page 13 and 14: Hexagonal Cells 13
Page 15: Example: K = 7 15
Page 18 and 19: Nyquist Bandwidth (for noiseless ch
Page 20 and 21: Signal-to-Noise Ratio • Ratio of
Page 22 and 23: Example of Nyquist and Shannon Form
Page 24 and 25: 24 HANDOFF IN CELLULAR SYSTEMS
Page 26 and 27: Handoff Decisions • Usually based
Page 28 and 29: Traditional Handoff Algorithms Choo
Page 30 and 31: Example Receiver Threshold 30
Page 32 and 33: Who and When • Who initiates hand
Page 36 and 37: High priority for Handoff • In no
Page 38 and 39: Queuing Handoff Calls (QHC) • Que
Page 40 and 41: Queuing Handoff Calls • QHC can b
Page 42: Other practical problems with hando

Mobile Cellular Systems - Alak Roy

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