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 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  e ►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  ►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