The Propagation Factor in Mobile Wireless Networks

1. The Propagation Factor in Mobile Wireless Networks Syed Aun Abbas LUMS SSE The Propagation Factor

2. Structure of the Talk • Aims to look at Mobile networks from numerous perspectives • Business considerations • Inter cell considerations • Intra cell considerations • System considerations • The focus is to understand issues and design considerations • Identify issues that still need attention and could form basis for future research The Propagation Factor

3. Business Considerations • Mobile operators own limited Bandwidth and limited Transmission Power. • They pay heftily for these resources • Want to sell services to the customers • Typical Services/Applications • Voice • Data • Real/Non-real time Video • Application Requirements are 1. Data Rate - symmetric or asymmetric 2. Latency – ( delay) 3. Bit Error Ratio The Propagation Factor

4. Business Considerations • Systems need to be designed to transform bandwidth and power in bits/sec of voice video and data that meets latency and bit error requirements • Do it in a manner that number of customers who can use these resources for payable applications should be maximized. • There are different dimensions to the last statement • Design a system that provides maximum useable bits per second for the whole system • This maximum capacity should be available to the subscriber base • A lot many time this capacity is not usable by the customers • Researchers continually try to find ways and means to improve upon system capacity and its utilization • Message to take home; System capacity is nearing limits but is utilization too? The Propagation Factor

5. INTERCELL CONSIDERATIONS: Maximizing Capacity of the Mobile Systems; • How can we achieve the objective? • Use Frequencies repeatedly • Use Digital Communication • Allows Compression • Allows easier multiplexing of the different tribes of services • Triple play > Voice/Data/video • Use Intelligent Control Techniques • Dynamic Channel Assignment uses resources smartly • Use Trunking The Propagation Factor

6. INTERCELL CONSIDERATIONS: Cellular Concept: Use Frequencies repeatedly The Propagation Factor

7. INTERCELL CONSIDERATIONS: Frequency Reuse - Cellular Concept • System capacity is co-channel interference limited • Carrier-to-Interference ratio (C/I) is the parameter of interest • Isolation derives from distance between cells using the same frequency group • Frequency planning • Split total bandwidth in N sets of k channels each • Allocate one channel set per cell without gaps and repeat • N increases, so does D and co-channel interference decreases • N increases, the number of channels per cell decrease and so does the system capacity • Problem is to find an optimum layout for an initial service that should be able to scale as system usage changes The Propagation Factor

8. INTERCELL CONSIDERATIONS: Frequency Reuse – Scaling the network • Cell splitting • Reduce antenna heights and transmit power • Do not upset the channel assignment scheme • Do not upset the SIR • Generally, reduce the radius to half • Practical implications remain • More handoffs, • CELL SECTORING • Use directional Antennas; Propagation can be in 120 or 60 degree sectors • Sectoring improves SIR by reducing the interference • More handoffs, however, as long as Base station handles handoff, MSC may be spared • Trunking efficiency may be reduced The Propagation Factor

9. INTERCELL CONSIDERATIONS: Frequency Reuse – Scaling the network • CELL ZONING > Kind of distributed base station > Still under active considerations • Addresses Trunking Inefficiency in Cell Sectoring • While 10 trunked channel with 0.01 GOS can support 4.46 Erlangs of Traffic, 2 groups of 5 trunked channels support 2.72 Erlangs of Traffic • Conclusion; It is desirable to have smaller cluster sizes with more channels/cell to maximize capacity • Any base station channel may be assigned to any zone • Making zones in a cell reduces the R in D/R and thus increases D/R while reducing Tx. power of the Cell • Radio Channel Assignment • Dynamic vs. Fixed • Fixed Channel Assignment – Calls blocked when all channels in use • Dynamic Channel Assignment does not allocate channel for cells permanently • Dynamic channel allocation takes into account likelihood of future blocking in the cells, the frequency of use, the reuse distance of the channel and other cost functions • Requires real time data on channel occupancy, traffic distribution and radio signal strength indications The Propagation Factor

10. INTRACELL CONSIDERATIONS: Maximize bits/sec/user/GPS coordinate Transceiver Design Issues • Transmit Signal Design - BW, Framing, Data Rate, Modulation • Signal Receiver Design - Coding, Interleaving, Diversity, Equalization etc. • All of the above have implications on how the radio waves are received at the receiver and what kind of issues are associated with them. Signal Propagation Issues • Path Loss Prediction - Large Scale Issues > Determine the receive signal strength • Other Channel Impairments: Fading, Doppler Frequency Shift and Delay Spread - Small Scale Issue • We know what are characteristics of the ideal transmission channel. Same loss at all frequencies and linear phase charter. The Propagation Factor

11. INTRACELL CONSIDERATIONS: Received Radio Signal at a Mobile • It has loss and variability in the loss The Propagation Factor

12. INTRACELL CONSIDERATIONS: Signal Propagation - Path Loss • Mobile cellular environment • Outdoor Environment • Macro, Micro and Pico Cells • Indoor Environment • Pico cells • Propagation Mechanism in Real Environments • Multipath Propagation • Reflection; • from the ground, building walls etc. • Reflection coefficient • Refraction; • through walls etc. • Diffraction; • because of edges of the buildings, hills etc. • Scattering; • because of Rough reflecting surfaces The Propagation Factor

13. INTRACELL CONSIDERATIONS: Different types of Fading and transmission rate/reach limitation Symbol duration, T FAST SELECTIVE FAST FLAT Tc SLOW SELECTIVE SLOW FLAT Signal Bandwidth Bc The Propagation Factor

14. INTRACELL CONSIDERATIONS: • From where all these impairments come from • Physics and environment geometry • Multipath propagation is the culprit (or hero in some cases; e.g., MIMO) • How can we get rid of these environments? • Can we really? The Propagation Factor

15. YES The Propagation Factor

16. INTRACELL CONSIDERATIONS: • Yes! WE CAN… • Antennas with adaptive beam forming can help • If we can reduce the beam width sufficient small; it virtually becomes free space path loss, fading due to multipath vanishes; ISI due to multipath vanishes, • MIMO will not yield gains anymore; But do we need them anymore? The Propagation Factor

17. Modulation and other radio interface are barely any different The Propagation Factor

18. SYSTEM CONSIDERATIONS; RF Coverage Optimization Issues Remain; Automate them further… • Focus Cell power resources where the users are; • Know the location of your users • Know the spatial distribution of the users • Know the temporal distribution of users per beam footprint • Beams should follow users temporal movement • How do we get the information from the users • Architectural and legal issues • Give rise to a new paradigm • May need overlaid open network management • How to ensure timely delivery with reliability? May need a complete new approach The Propagation Factor

19. SYSTEM CONSIDERATIONS:Mobile Network Architecture; GSM Networks VLR HLR PSTN Um AC MAPn Voice MS EIR Abis MAPn BTS A ISDN MS Voice/ Data BSC MSC HLR- Home Location Register VLR - Visitor Location register MSC - Mobile Switching Center BSC - Base Station Controller BTS - Base Transceiver Station AC - Authentication Center EIR - Equipment Identity Register Data BTS Internet The Propagation Factor

20. SYSTEM CONSIDERATIONS: GSM System - Protocol Architecture Base Station System - BSS MS BTS BSC MSC CM Q.931+ ISUP TUP MM CM DTAP, BSSMAP BSSMAP, DTAP MM SCCP SCCP RR RR BTSM BTSM MTP3 MTP3 MTP3 LAPDm LAPDm LAPD LAPD MTP2 MTP2 MTP2 TDMA TDMA T1/E1 or L1 T1/E1 or L1 MTP1 MTP1 MTP1 Um Abis A MAPn To from other MSCs and networks To from other MSCs The Propagation Factor

21. 3rd Gen. Mobile Networks - IMT 2000 MS BTS BSC MSC CM BSCM SCCP CM BSM CM BSM CM MTP3 MM RR RELAY RR Q.2140 BSM RELAY LAC LAC Q.SAAL LAC Q.SAAL LAC Q.SAAL TDMA PHY AAL/ATM/PHY AAL/ATM/PHY PHY AAL/ATM/PHY Um Abis A MAPn To from other MSCs and networks APPLICATION MAP(HLR) To from other MSCs TCAP TCAP - TCP/UDP Convergence SCCP MTP3 Q.2140 TCP UDP Q.SAAL IP AAL/ATM/PHY PHY HLR The Propagation Factor

22. SYSTEM CONSIDERATIONS: 4G LTE IP basedSystem Architecture The Propagation Factor

23. THANKS and GOOD LUCK The Propagation Factor

24. ABSTRACT • The mobile communication services market is now focused on delivering data services which have come a long way from short messaging and paging services. WiMax and LTE are leading contenders to proliferate the mobile data networks market. With most of the technology feature being very similar, the winning attributes of the two technologies are not related to their own technical virtues but are elsewhere. In this talk, we would provide a perspective on how propagation plays a significant role in that determination. We would also attempt to identify some areas of continuing research that should be most useful to impact the future of mobile data networks. The Propagation Factor