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Wireless Networks

Wireless Networks. Lecture 44 4G Issues Dr. Ghalib A. Shah. Outline. 4G Overview Heterogeneous Wireless networks Evolution Issues in 4G Mobility Management Handoffs Types, VHO process, VHO Issues Standards QoS Considerations. Last Lecture. Reference Model Burst profiles

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Wireless Networks

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  1. Wireless Networks Lecture 44 4G Issues Dr. Ghalib A. Shah

  2. Outline • 4G Overview • Heterogeneous Wireless networks • Evolution • Issues in 4G • Mobility Management • Handoffs • Types, VHO process, VHO Issues • Standards • QoS Considerations

  3. Last Lecture • Reference Model • Burst profiles • Convergence sublayers • MAC PDU format • MAC PDU Transmission • Fragmentation / Packing • Request/Grant Scheme • Classes of Uplink service • Power management/Handoff

  4. 4G Overview • 4G mobile communication systems tend to mean different things to different people: • for some it is merely a higher-capacity new radio interface, • while for others it is an inter-working of cellular and wireless LAN technologies that employs a variant of the Mobile IPv6 mobility management protocol for inter-system handoff. • There is no doubt that 4G systems will provide higher data rates. Traffic demand estimates suggest that, to accommodate the foreseen amount of traffic in the 2010 – 2020 timeframe in an economically viable way, 4G mobile systems must achieve a manifold capacity increase compared to their predecessors. • researchers and vendors are expressing a growing interest in 4G wireless networks that support global roaming across multiple wireless and mobile networks • a system that enables an “Always Best Connected” – or “ABC”

  5. There are many wireless network technologies Cellular networks, Wireless LANs, Wireless PANs, mobile Wimax, etc. • 4G networks will play a key role for integrating various network architectures and technologies and achieving a seamless wireless access infrastructure • 4G provides high-speed, large volume, good quality, and global coverage to roam between different types of technologies

  6. It is widely accepted that the individual (wireless and/or wireline) access networks will interface to core and/or backbone network elements over the IP protocol • these wireless access networks are expected to have the following in common: • A dynamic address assignment mechanism (e.g., DHCP, SLP, IPv6) that is capable of associating a short-lived or long-lived IP address to the respective wireless interface at the mobile terminal (e.g., Mobile IP COA association) • A transparent IP forwarding service that is accessible over the logical termination of the IP layer at the mobile terminal and one or more gateways

  7. Heterogeneous Wireless Networks • A mixture of co-existing radio access technologies. • Different access technologies (radio interfaces) and overlapping coverage. • Different network architectures and protocols for transport, routing and mobility management. • Different service demands from mobile users (low-data rate, high-data rate, voice, multimedia, etc) • Different operators in the market.

  8. Evolution of 4G

  9. Heterogeneous Networks

  10. Issues in 4G • Need to resolve issues as • Access • Handoff • Location coordination • Resource coordination to add new users • Support for multicasting • Support for quality of service • Wireless security and authentication • Network failure and backup • Pricing and billing.

  11. Mobility Management • Mobility Management • Location Management: enables system to track location of mobile terminal (MT) • Location updates and paging • Handoff Management: the process by which an MT keeps its connection when it moves from one point of attachment (base station or access point) to another

  12. Handoff Management • Low signalling and processing overhead. • Minimum packet loss and delay (seamless HO). • Guaranteeing QoS during the process and transfer of context. • Use of any “triggers” or metrics available to decide when and where. • Efficient use of network and MT resources. • Enhanced scalability, reliability and robustness. • Allow inter-technology handoff (VHO).

  13. Handoff Types • Homogeneous (Horizontal) Handovers • Within Single Network (Localized Mobility) • Limited opportunities • Mainly use received signal strength (RSS) to decide handoff • Heterogeneous (Vertical) Handovers • Across Different Networks (Global Mobility) • More Opportunistic • Handoff metric: RSS, offered bandwidth, price, power consumption, speed, …….

  14. Vertical handoff process • Step 1: “System Discovery” • Step 2: “Handoff Decision” • Step 3: “Handoff Execution”

  15. Step 1: “System Discovery” • MT must know which • wireless networks are reachable. • Periodic beacons from AP. • Signal measurements. • Handoff metrics (network information) gathering: Bandwidth, cost, delay, SNR, power, etc. • Periodic network scanning. • All interfaces always on.

  16. Step 2: “Handoff Decision” • MT then evaluates the • Some example policies: • “Always use the cheapest network”. • “Always use the interface with lower power consumption”. • “Always use the WLAN”. • “Always use the network with more bandwidth”. • Decision may be based on utility / cost functions.

  17. Step 3: “Handoff Execution” • If MT decides to perform a VHO, it executes the VHO procedure required to be associated with the new wireless network.

  18. VHO Issues • When to switch? • VHO policies • WLAN to Cellular ≠ Cellular to WLAN • Seamless handoff • Packet loss and VHO latency. • Load balancing between networks. • QoS guarantees • Security and Authentication. • Billing • Implementation.

  19. Standardization Efforts • IETF • Mobility for IPv4 (MIPv4) • Mobility for IPv6 (MIPv6) • Mobility for IP: Performance, Signalling and Handoff Optimization (MIPSHOP) • IEEE 802.21 Media Independent Handover Group is working toward the seamless handoffs between IEEE 802.XX family and 3G Cellular • 3GPP and 3GPP2 are working in inter-working with WLAN as an extension of their radio access networks. • Loosely Coupled Architecture • Tightly Coupled Architecture

  20. Tightly coupling • Provides common charging and billing service • Provides mobility support using traditional 3G technology • Reuses 3G service (e.g., SMS, MMS, etc.) • Causes large traffic load in 3G core network • Loosely coupling • Provides simple integration approach • Needs minimal requirement on the access network • Provides independent network management

  21. QoS • Supporting QoS in 4G networks will be a major challenge due to varying bit rates, channel characteristics, bandwidth allocation, fault-tolerance levels, and handoff support among heterogeneous wireless networks. • QoS support can occur at the • Packet, • Transaction • Circuit • User

  22. Packet-level QoS • applies to jitter, throughput, and error rate. • Network resources such as buffer space and access protocol are likely influences. • Transaction-level QoS • describes both the time it takes to complete a transaction and the packet loss rate. • Certain transactions may be time sensitive, while others cannot tolerate any packet loss.

  23. Circuit-level QoS • includes call blocking for new as well as existing calls. • It depends primarily on a network’s ability to establish and maintain the end-to-end circuit. • User-level QoS • depends on user mobility and application type. • The new location may not support the minimum QoS needed, even with adaptive applications.

  24. End-to-End QoS • Developers need to do much more work to address end-to-end QoS. • They may need to modify many existing QoS schemes, including admission control, dynamic resource reservation, and QoS renegotiation to support 4G users’ diverse QoS requirements. • A wireless network could make its current QoS information available to all other wireless networks in either a distributed or centralized fashion so they can effectively use the available network resources. • Additionally, deploying a global QoS scheme may support the diverse requirements of users with different mobility patterns.

  25. QoS Parameters • 802.11e • Nominal MSDU size • Min/mean/max data rate • Mean/max service interval • Traffic type (isochronous, asynchronous) • Burst size • UMTS (Release 5) • Traffic class(conversational, streaming, interactive, or background) • Guaranteed, maximum bit rate • Maximum SDU size • SDU/bit error ratio • Transfer delay • 802.16-2004 • Traffic priority • Maximum sustained traffic rate • Maximum traffic burst • Minimum reserved traffic rate • Scheduling type (best-effort, non-real time polling, real-time polling, unsolicited grant) • Tolerated jitter, maximum latency

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