4G Wireless Systems. Outlines. Data Rates of Wireless Networks. Wireless Networks. Wireless Networks Throughput versus Range

Transcription

1 Outlines 4G Wireless Systems Vijay K. Garg, Ph.D., P.E. Department of Electrical & Computer Engineering, College of Engineering, University of Illinois at Chicago Types of wireless networks Evolution of 2G to 3G and their limitations 4G networks and their visions 4G design concepts 4G architectures 4G technologies 4G status 07/2005 CSCC 2005 (VKG) 1 07/2005 CSCC 2005 (VKG) 2 Wireless Networks Data Rates of Wireless Networks Based on coverage, data rate and power consumption, we can classify the wireless networks as: Types of Wireless networks Wireless Personal Area Network (WPAN) Wireless Local Area Network (WLAN) Wireless Metropolitan Area Network (WMAN) Wireless Wide Area Network (WWAN) Short Range: Low Power, Personal Area Bluetooth (1 Mbps) Ultra Wideband (UWB) (100 Mbps) Middle Range: Medium Power, Local Area Long Distance: High Power, Wide Area 2G GSM (9.6 kbps) PDC GPRS (114 kbps) PHS (64 kbps, up to 128 kbps) 3G (CDMA2000, WCDMA) (384 kbps to 2 Mbps) Home RF (10 Mbps) IEEE802.11a,b,g (108 Mbps) [ a based proprietary 2x mode ] 07/2005 CSCC 2005 (VKG) 3 07/2005 CSCC 2005 (VKG) 4 Wireless Networks Throughput versus Range 2G and 3G Cellular Networks 07/2005 CSCC 2005 (VKG) 5 07/2005 CSCC 2005 (VKG) 6 1

2 Limitations of Current 2G and 3G Systems What is 4G System? Limited functionalities in a single handset Short message, fax, Internet (text), voice Limited global roaming Not available to non-gsm users In US: IS-95 CDMA In Japan: PDC and PHS TDMA users Singular point of failure can affect the whole network, no load balancing, and low spectral efficiencies With increasing data rate, the output power must be increased or size of cell will have to be decreased to support higher data rates 4G originally conceived by Defense Advanced Research Projects Agency (DARPA) (designer of Internet) DARPA selected the distributed architecture, end-toend Internet Protocol (IP), and peer-to-peer networking (every device is both a transceiver and a router for other devices in the network eliminating spoke-and-hub architecture weakness of cellular systems) Network coverage/ capacity dynamically changes to accommodate changing user patterns Users automatically move away from congested routes to allow network to dynamically and automatically self-balance 07/2005 CSCC 2005 (VKG) 7 07/2005 CSCC 2005 (VKG) 8 Reasons for 4G Systems Definition of 4G System Difficulty of CDMA to provide higher data rates Need for continuously increasing data rate and bandwidth to meet multimedia requirements Limitation of spectrum and it s allocations Inability to roam between different services To provide a seamless transport for end-to-end mechanism To introduce a better system with reduced cost 4G can be defined as Wireless Ad hoc peer-to-peer networking with High usability and global roaming End user terminals should be compatible with any technology, at any time, any where in the world Distributed computing Personalization This means that any type of person should be able to access services. The service providers should be able to provide customized services to different users. Multimedia Support The user should be able to receive high data rate services. This demands higher bandwidth and higher data rates. 07/2005 CSCC 2005 (VKG) 9 07/2005 CSCC 2005 (VKG) 10 4G Visions and Goals 4G System from a User s Perspective A flexible, low-cost general packet data system to allow wide-area coverage and high mobility Perceived performance 100 Mbps Ethernet High spectral efficiency (10-15 times increase over 3G) QoS and fairness A system based on adaptive resource allocation Higher frequency bands than 3G (< 5 GHz preferred) RF channel bandwidth of MHz Bandwidth between MHz (paired or unpaired) International 4G spectrum allocation. Multiple functionalities in a single handset Voice, bulk data transfer, image, short message, fax, web surfing, video conferencing/broadcasting and future applications, etc. Global roaming A single universal identification access number Seamless access, transparent billing, security Low cost in service and handset 07/2005 CSCC 2005 (VKG) 11 07/2005 CSCC 2005 (VKG) 12 2

3 4G System Requirements Main Challenges of 4G Higher bit rates than 3G (20 Mbps < peak < 200 Mbps) Higher spectral efficiency and lower cost per bit than 3G Air interface and MAC optimized for IP traffic (IPv6, QoS) Adaptive modulation/coding with power control, hybrid ARQ Smaller cells, on average, than 3G Resource allocation: multiplexing heterogeneous, busty data traffic QoS guarantee for bandwidth and/or delay sensitive applications User channel scheduling Code assignment in CDMA Interoperability with 2G and 3G Ubiquitous deployment: indoor and outdoor cell coverage Convergence with backbone (wire line) networks Multimode user terminals The user terminals should be able to configure themselves in different modes. This eliminates need of multiple terminals. Wireless System Discovery and Selection The terminal should be able to select the desired wireless system. The system could be WLAN, GPS, WWAN etc. Terminal mobility Both horizontal and vertical handoff should be supported (see next slide) Personal mobility No matter where the user is located and what device he/she is using, he/she should be able to access his messages. Security and Privacy The existing security systems are designed for specific services and do not provide flexibility for the users. New security systems are needed for 4G Fault Tolerance With a tree like topology in the existing system, if one of the components fails, the whole system goes down, we need a fault tolerance system Billing System Need to design a billing architecture to provide a single bill to the user for all services he/she has used. The bill should be fair to all kinds of users. 07/2005 CSCC 2005 (VKG) 13 07/2005 CSCC 2005 (VKG) 14 4G Design Concepts Use short term properties of the channel instead of averaging Use multiple antennas at base station and mobile station Scheduling among sectors and users (combined MAC and Radio Resource Management) Improve performance on TCP level, allow Interlayer (OSI) interaction/communication Multimode user terminals Proposed Architectures for 4G How to access several different mobiles and wireless networks? Three possible solutions: Multimode Devices Overlay Architecture Common Access Protocol 07/2005 CSCC 2005 (VKG) 15 07/2005 CSCC 2005 (VKG) 16 Multimode Devices Overlay Network A Single terminal with multiple interface to access different systems Device incorporates required hardware to access different technologies Does not require any network modification Increases complexity of user device, user device will be expansive QoS handling for this type of architecture remains an open issue. 07/2005 CSCC 2005 (VKG) 17 User accesses an overlay network consisting of several universal access points (UAP) UAP selects an access point depending on user choice, availability and desired Qos Major operations such as handoff, frequency translation, content adaptation etc are performed by overlay network. Overlay network suffers an increase in complexity 07/2005 CSCC 2005 (VKG) 18 3

4 Common Access Protocol 4G System: Convergence with Backbone Network Infrastructure Issues infrastructure link to last mile: ATM, WDM flow control at access points / network edges packet routing: native-mode ATM, TCP/IP, mobile IP end-to-end QoS control: minimum bandwidth guarantee integration with various application-specific network: interworking Can be used if a wireless network can support one or two different protocols One possible solution is to use ATM, which might need interworking between different networks. To implement ATM, all wireless networks must be capable of supporting ATM cells with additional headers. 07/2005 CSCC 2005 (VKG) 19 07/2005 CSCC 2005 (VKG) 20 4G System: Issues to be Resolved 4G System: Issues to be Resolved Multiplexing of heterogeneous traffic (resource allocation): Multiple information bearing data rates (> 2 Mbps) QoS guarantee (BER, delay, power/spectral efficiency) Cell coverage environment (indoor, outdoor, local and wide area) Flexibility and efficiency in channel assignment and scheduling Complexity and power consumption of a transceiver Seamless Access and Global Roaming Smooth integration from 2G and 3G systems Allocation of (high frequency) universal frequency bands Requirement for multi-band, multi-mode transceiver units (e.g. software radio, advanced signal processing techniques) Handoff between different cell environment or wireless systems (vertical handoff) 07/2005 CSCC 2005 (VKG) 21 07/2005 CSCC 2005 (VKG) 22 Vertical and Horizontal Handoff Wireless Network Evolution Horizontal Handoff: Traditional handoff performed by a mobile Vertical Handoff: Handoff when a user switches from one network to totally different network. 1G to 4G 1G Analog AMPS TACS NTT etc b/s/hz Max. rate 64 kbps 2G Digital modulation Convolution coding Power Control PDC GSM IS-95 PHS etc b/s/hz Max. rate 2 Mbps 3G WCDMA Turbo-coding EDGE WCDMA cdma2000 etc. 3 4 b/s/hz? Max. rate ~ 200 Mbps 4G Smart Antennas? MIMO? Adaptive System OFDM Modulation 07/2005 CSCC 2005 (VKG) 23 07/2005 CSCC 2005 (VKG) 24 4

5 Technologies for 4G Better channel assessment IP Networking Integration and Interworking Scheduling Multi-carrier CDMA (MC-CDMA) OFDM Software Radio Adaptive Antennas MIMO Technologies for 4G Instantaneous channel condition estimations of several users to distribute transmission loads where it pays off most Better access technologies than 3G MC-CDMA (hybrid of CDMA and OFDM) Fast Low-latency Access with Seamless Handoff (FLASH)- Orthogonal Frequency Division Multiplexing (OFDM) Adaptive Antenna 4 to 8 elements at base station 2 elements at terminal Adaptive coding and modulation Adaptive channel/code allocation Scheduling among sectors and users 07/2005 CSCC 2005 (VKG) 25 07/2005 CSCC 2005 (VKG) 26 Single Link with Feedback Multiple In Multiple Out (MIMO) Coding Modulation Fading Channel Detection Channel Estimation MIMO (Multiple-in, multiple-out) takes advantage of multiplexing to increase wireless bandwidth and range. MIMO algorithms send information out over two or more antennas and the information is received via multiple antennas as well. On normal radio, multiplexing would cause interference, but MIMO uses the additional pathways to transmit more information and then recombines the signal on the receiving end. Rate Adaptation Feedback provides: adaptive coding and modulation adaptive channel resource allocation Channel Prediction MIMO systems provide a significant capacity gain over conventional single antenna systems, along with more reliable communication. The benefits of MIMO lead many to believe it is the most promising of emerging wireless technologies. 07/2005 CSCC 2005 (VKG) /2005 CSCC 2005 (VKG) 28 Interworking Strategies Mobile IP Approach Hot-spot area such as a building, a railway station, or an airport is normally covered by a number of network To provide seamless roaming between heterogeneous networks interworking is required. Three approaches to interconnect high-tier (GPRS, 3G) and low-tier (WLAN) systems: Mobile IP Approach Gateway Approach Emulator Approach Also known as loose coupling approach Introduces mobile IP (MIP) to two networks Requires to install MIP devices HA and FA in both networks Provides IP mobility for roaming between two networks Since user device requires to send registration back to home network, packet delay and lose are problems for handovers 07/2005 CSCC 2005 (VKG) 29 07/2005 CSCC 2005 (VKG) 30 5

6 Mobile IP Approach Gateway Approach Introduces a new logical node to connect two networks; the node is located in between two networks and acts as internal device of two networks. Logical node exchanges necessary information between networks, converts signals, and forwards packets for roaming users. Separates operations of two networks; two networks handle their subscriber independently. Two networks operate independently; packets for roaming users go through the node without processing by MIP; and handoff delay and lose are reduced. 07/2005 CSCC 2005 (VKG) 31 07/2005 CSCC 2005 (VKG) 32 Gateway Approach Emulator Approach Uses WLAN as an access stratum in a 3G network; replaces 3G access stratum by WLAN layer 1 and layer 2 MIP is not required All packet routing and forwarding are processed by a 3G core network. Packet lose and delay are much reduced Lacks flexibility since two networks are tightly coupled Operators of two networks should be same in order to exchange lots of information 07/2005 CSCC 2005 (VKG) 33 07/2005 CSCC 2005 (VKG) 34 Emulator Approach 4G Systems : A Possible Scenarios 3G systems will support voice services To alleviate congestion in 2G To support ever growing population of mobile users 3G systems will provide limited service for multimedia applications voice services a combination of bandwidth and delay sensitive traffic 2G, 3G and 4G systems must interoperate and coexist 2G and 3G systems will be key providers of voice services 4G systems will carry mainly non-voice traffic Integration with private local WLAN and WATM networks Direct access and interfacing with fixed backbone network 07/2005 CSCC 2005 (VKG) 35 07/2005 CSCC 2005 (VKG) 36 6

7 Applications of 4G Virtual Presence 4G will provide user services at all times, even if the user is off-site Virtual Navigation 4G will provide users with virtual navigation through which a user can access database of the streets, buildings etc of a large city. This requires high speed data transmission Tele-medicine 4G will support remote health monitoring of patients via videoconference assistance for a doctor at anytime and anywhere Tele-geo-processing Applications Combination of geographical Information System (GIS) and GPS in which a user get the location querying Education 4G will provide a good opportunity to people anywhere in the world to continue their education on-line in a cost effective manner Status of 4G Still in a formative stage (possible commercial application in 2010) ITU WG 8F beginning to consider the requirements 07/2005 CSCC 2005 (VKG) 37 07/2005 CSCC 2005 (VKG) 38 7