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Cellular Networks

Cellular Networks. Lecture 6 Paul Flynn. Cellular Telephony - Architecture. Very Basic Cellular/ PCS Architecture. Mobility Database. Public Switched Telephone Network. Base Station Controller. Mobile Switching Center (MSC). Radio Network. Base Station (BS). Mobile Station.

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Cellular Networks

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  1. Cellular Networks Lecture 6 Paul Flynn

  2. Cellular Telephony - Architecture

  3. Very Basic Cellular/PCS Architecture Mobility Database Public Switched Telephone Network Base Station Controller Mobile Switching Center (MSC) Radio Network Base Station (BS) Mobile Station

  4. Duplex Communication - FDD • FDD: Frequency Division Duplex Base Station B Mobile Terminal M Forward Channel Reverse Channel Forward Channel and Reverse Channel use different frequency bands

  5. Frequency Frequency Time Time Frequency Time Access Methods FDMA TDMA CDMA

  6. Clusters • A cluster is a group of cells • No channels are reused within a cluster A seven Cell Cluster

  7. Example - Frequency Spectrum Allocation in U.S. Cellular Radio Service Reverse Channel Forward Channel 991 992 … 1023 1 2 … 799 991 992 … 1023 1 2 … 799 824-849 MHz 869-894 MHz Channel Number Center Frequency (MHz) Reverse Channel 1 <=N <= 799 991 <= N <= 1023 0.030N + 825.0 0.030(N-1023) + 825.0 Forward Channel 1 <=N <= 799 991 <= N <= 1023 0.030N + 870.0 0.030(N-1023) + 870.0 (Channels 800-990 are unused) Channel bandwidth is 45 MHz

  8. Frequency Reuse • Only a small number of radio channel frequencies were available for mobile systems • Therefore engineers had to find a way to reuse radio channels to carry more than one conversation at a time • The solution the industry adopted was called frequency reuse. Implemented by restructuring the mobile telephone system architecture into the cellular concept

  9. Frequency Reuse • The concept of frequency reuse is based on assigning to each cell a group of radio channels used within a small geographic area • Cells are assigned a group of channels that is completely different from neighbouring cells • The coverage area of cells is called the footprint and is limited by a boundary so that the same group of channels can be used in cells that are far enough apart

  10. Frequency Reuse • Cells with the same number have the same set of frequencies Frequency Reuse

  11. f2 f7 f3 f1 f6 f4 f5 Frequency Reuse using 7 frequencies allocations f2 f7 f3 f1 f6 f4 f2 f5 f2 f7 f3 f7 f3 f1 f2 f1 f6 f4 f7 f3 f6 f4 f5 f1 f5 f6 f4 f5 Each cell is generally 4 to 8 miles in diameter with a lower limit around 2 miles.

  12. Cell Splitting • Allows urban centres to be split into as many areas as necessary for acceptable service levels in heavy-traffic regions, while larger, less expensive cells can be used to cover remote rural regions

  13. Cellular Concept with Sectors frequency re-use base station

  14. Hand-off • The final obstacle in the development of the cellular network involved the problem created when a mobile subscriber moved from one cell to another during a call

  15. Looking to PCS from different Angles Internet PSTN (Telephone Network) Wireless Access • Mobile Users • Laptop users • Pocket PC users • Mobile IP, DHCP enabled computers • Mobile Users • Cell phone users • Cordless phone users Telecom People View Data Networking People View

  16. Telecom and Data Networking Telecom Interest Data Networking Interest • - Voice Transmission • - Frequency Reuse • Handoff Management • Location Tracking • Roaming • QoS • GSM, CDMA, Cordless Phones, • GPRS, EDGE • Data Transmission • Mobile IP (integrating mobile hosts to internet) • Ad-hoc Networks • TCP over Wireless • Service Discovery • Radio Propagation • Link Characteristics • Error Models • -Wireless Medium • Access (MAC) • - Error Control

  17. Major Mobile Radio Standards USA

  18. Major Mobile Radio Standards - Europe

  19. Example - Frequency Spectrum Allocation in U.S. Cellular Radio Service Reverse Channel Forward Channel 991 992 … 1023 1 2 … 799 991 992 … 1023 1 2 … 799 824-849 MHz 869-894 MHz Channel Number Center Frequency (MHz) Reverse Channel 1 <=N <= 799 991 <= N <= 1023 0.030N + 825.0 0.030(N-1023) + 825.0 Forward Channel 1 <=N <= 799 991 <= N <= 1023 0.030N + 870.0 0.030(N-1023) + 870.0 (Channels 800-990 are unused) Channel bandwidth is 45 MHz

  20. 2G Technologies

  21. GSM Speech Signal Processing

  22. GSM and CDMA Coverage Map Worldwide

  23. What is WiMax? • Worldwide Interoperability for Microwave Access • Last mile wireless broadband access • Alternative to cable and DSL • Deliver data, voice, video • Support hundreds to thousands of homes/business

  24. Defined by IEEE as 802.16 • Typical target environment: • Targets fixed, portable, and mobile stations • Environments with and without line of sight • Cell radius of 3-10 kilometers • Capacities of up to 40 Mbps per channel • Mobile network deployments of up to 15 Mbps, 3 km radius

  25. Builds on andExtends WiFi Technology • Advantages of WiFi are: • Easy to deploy, unlicensed spectrum, low cost • Supports (limited) mobility • But WiMax needs to address the following:

  26. WiFi limitations • Susceptible to interference • 802.11 targets short-range indoor operation (mostly) • Security is a concern • Limited level of mobility • WiMax is intended to complement WiFi • WiMax Forum: promotes WiMax and looks after interoperability

  27. WiMax Deployment

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