Moving Behavior Moving Behavior ( 1 , 1 , S 1 ) ( 2 , 2 , S - PDF document

Mobility Support & Channel Reuse Mobility Support & Channel Reuse ob ob ty Suppo t & C a ty Suppo t & C a e e euse euse 無線網路多媒體系統 無線網路多媒體系統 Mobility Support~ Handover M bili S H d Wireless Multimedia System Lecture 5: Cellular Concepts 中央大學 吳曉光博士 中央大學 吳曉光博士 http://wmlab.csie.ncu.edu.tw/course/wms Channel Allocations: Reuse Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory ChungLi Case Study C u g C u g ChungLi Case Study Case Study Case Study Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Moving Behavior Moving Behavior ( μ 1 , σ 1 , S 1 ) ( μ 2 , σ 2 , S 2 ) ( μ 3 , σ 3 , S 3 ) ( μ 4 , σ 4 , S 4 ) Call arrive l 6 l 6 l l 7 l 6 l 5 l 4 l l l l 5 l 7 l 5 l 6 l 3 l 7 l 4 l 3 l 2 l 4 l 2 l 8 l l l 8 l 14 l 1 l 1 l 13 l 14 l 12 l 13 l 12 l 9 12 13 12 9 l l 9 l 10 l 11 l 11 l 10 Time Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory

Channel Assignment in Cellular System C a Channel Assignment in Cellular System C a e e ss g ss g e t e t Ce u a Syste Ce u a Syste Hand-off in Cellular Networks Hand a d o a d o off in Cellular Networks Ce u a Ce u a et o et o s s � Fundamental Problem: � Transfer of mobile to a new channel when it crosses cell boundary � Fixed Channel Assignment � Handoff delay � Dynamic Channel Assignment � Prioritizing handoffs to reduce probability of dropped calls � Hybrid Schemes � Handoff Strategies � Whole Channel Usage (CDMA) � Network Controlled handoff (NCHO) � Reduce the Cell Size � Mobile assisted handoff (MAHO) � Mobile controlled handoff (MCHO) Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Agenda Agenda ge da ge da Reading Reading ead ead g g � Cellular Concepts � [Katzela96]Katzela, and M. Nahgshineh ”Channel assignment Nahgshineh, Channel assignment � Channel Assignments schemes for cellular mobile � Handover telecommunication systems: a comprehensive survey ” IEEE comprehensive survey, IEEE � Next Lecture: 3G WCDMA design Personal Communications, June 1996 � [P lli i 96] G P P lli i “T � [Pollinin96], G.P. Pollini, “Trends in d i handover design, “IEEE Communications Magazine, March 1996 1996. Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Cellular System Concept Cellular System Concept C a Channel Allocation C a Channel Allocation e e ocat o ocat o MSC PSTN Pre-Cellular Post-Cellular � A given Channel Spectrum (or bandwidth) can be divided into a set of di j i t disjoint or non-interfering radio channel i t f i di h l • Frequency Division � frequency band q y • Time Division � time slot � Replace single high power transmitter covering the entire service area • Code Division C d Di i i with low power ith l � modulation code • Mobiles in sufficiently distant base-stations may be assigned identical channel (frequency, time slot, & code) • System capacity may be increased without adding more spectrum � Major conceptual breakthrough in spectra congestion & user capacity • Required relatively minor technological changes frequency reuse & co- channel interference, channel allocation, hand-offs Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory

Cell Shape Ce Ce Cell Shape S ape S ape Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory

Channel Reuse Channel Reuse C a C a e e euse euse � The same channel is reused simultaneously by other sets (Co- channel) h l) k k k − α α signal i l P P d d = = t t CIR ∑ − α + int erference P d N k i 0 Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Interference Interference te e e ce te e e ce How to improve CIR (Quality) How to improve CIR (Quality) o o to to p o e C p o e C (Qua ty) (Qua ty) � Increase the transmitting power (Power Control) � Increase the separating distance (Channel Reuse) − α signal P d = = CIR t t ∑ 5 − α + int erference P d N i i 0 1 − α signal P d = = t t CIR ∑ ∑ α int erference f P d N i i 0 0 Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory Approaches Approaches pp oac es pp oac es Frequency Reuse Frequency Reuse eque cy eque cy euse euse � Each BS is allocated a subset of carrier freqs � Fixed no flexibility 6 5 4 � Nearby BSs are allocated a different subset to Nearby BSs are allocated a different subset to 6 4 avoid interference 1 7 3 � The total set is allocated to a small tesselating � Dynamic complexity 2 group of N neighboring BSs group of N neighboring BSs 2 2 • 5 Called “reuse cluster” 6 � Hybrid might be ok 4 • 1/N is the “reuse factor” 1 Area • service System capacity goes up by System capacity goes up by 7 7 3 3 N × N Area A cell 2 � Used in FDMA & TDMA based systems • Not required in CDMA which has universal frequency 6 5 5 reuse reuse 4 � Cells idealized as hexagons • Real cell footprints are amorphous Idealized grid of 2 • • Hexagon close to a circle Hexagon close to a circle Hexagonal cells • Not appropriate for micro-cells, highways etc. Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory ™ Wireless & Multimedia Network Laboratory Wireless & Multimedia Network Laboratory