Transcript Issues
3G NETWORKS Abhinay Kontham Introduction to 3G Why 3G? Next few slides taken from web – give various reasons as to why 3G was needed. Why do you think 3G was created? Why 3G? Existing mobile networks (GSM/CDMA) were designed to handle voice traffic and voice-oriented services. Then, when they were introduced into the market it turned out that, other than voice-oriented, additional services (SMS to set an example) gained unexpected popularity. The need for data transmission through mobile networks has been growing gradually together with Internet popularity. Why 3G? Therefore some network upgrades had to be introduced into existing mobile networks (HSCSD, GPRS). However, these improvements provide only limited capability (e.g. GPRS - up to 50kbit/s in reality). They don't provide flexible, variable data speed, supporting Quality of Service solutions. Lack of Resources Another important factor is that together with the need for efficient data-oriented mobile networks, the beginning of radio resources shortage in dense populated areas has been observed, due to high level of penetration in mature mobile markets (penetration rates around 50% and up to 80% in the Nordic countries). Therefore a new radio access technology is needed to cope with those problems. 3G Vision Multimedia (voice, data & video) Increased data rates 384 Kbps while moving 2 Mbps when stationary at specific locations Universal global roaming Increased capacity (more spectrally efficient) IP architecture 3G Services: “The Promise” Customised Infotainment Multimedia Messaging Service Mobile Intranet/Extranet Access Mobile Internet Access Location-based Services Rich Voice (simple and enhanced voice) Designing 3G Technical arguments galore as to which technologies should be used. Standardisation bodies tried to come to agreement as to what was the best options The Standards Issue When the ITU tried to unify and standardize 3G technologies, no consensus was reached. There were thus five terrestrial standards developed as part of the IMT-2000 program. Instead, depending on where in the world 3G will be implemented, the 3G standard will be based on CDMA variants with some other technologies thrown in as well. IMT-2000 Terrestrial Radio Interfaces Standards adopted for IMT2000 Mode IMT-DS Description DIRECT SEQUENCE IMT-MC MULTICARRIER IMT-TC TDMA/CDMA IMT-SC IMT-FT SINGLE CARRIER FDMA/TDMA Standard W-CDMA UTRA FDD cdma2000 UTRA TDD TD-SCDMA UWC-136 DECT *the three indicated in green are emerging as the most important Migration To 3G 3G 2.75G Intermediate Multimedia 2.5G Multimedia Packet Data 2G Digital Voice 1G Analog Voice GPRS GSM EDGE W-CDMA (UMTS) 384 Kbps Up to 2 Mbps 115 Kbps NMT 9.6 Kbps GSM/ GPRS TD-SCDMA (Overlay) 115 Kbps 2 Mbps? TDMA TACS 9.6 Kbps iDEN 9.6 Kbps iDEN PDC (Overlay) 9.6 Kbps AMPS CDMA 1xRTT CDMA 14.4 Kbps / 64 Kbps PHS 1984 - 1996+ 1992 - 2000+ cdma2000 1X-EV-DV PHS (IP-Based) 144 Kbps 64 Kbps 2001+ 2003+ Over 2.4 Mbps 2003 - 2004+ Source: U.S. Bancorp Piper Jaffray Issues REGIONAL BLACKOUTS APPLICATIONS TESTING IMPACT OF VOICE AND DATA TRAFFIC ON THE NETWORK Regional Blackouts Protection of broadcast content on 3G Networks One of the driving forces behind the development of 3G systems is the potential to deliver complex content to consumers. There is a growing collaboration between broadcast and mobile network providers. The challenge in providing such a service is content protection. CONTENT PROTECTION Advances in mobile communication technology have provided the many services to the subscribers at any location. The removal of barriers to the delivery of such services raises the issues of content protection and digital rights management. Broadcasters are often required to restrict broadcast of certain content to specific geographic locations , or specific dates and times CURRENT PROBLEM IN 3G NETWORKS. The location of the end devices in the network can be tracked using satellites and GPS technology but , this is a very costly solution for tracking low cost mobile devices without satellite reception. The problem is compounded where the receivers have the ability to store and forward content. TRUSTED HARDWARE SOLUTION An obvious way to provide trustworthy location data is to use a hardware that is trusted by the content provider. This can be done by using a GPS system but it is an expensive method to implement. Alternatively, the end device could be connected to the trusted part of the intermediate network. The network can then provide the current location and time of the gateway from which the end device is receiving on a special request. the problem wit this methodology is that it restricts to the end device which can be directly connected to the trusted network. NETWORK MODEL Issue -2 APPLICATIONS TESTING The 3G networks demand for test and verification methods that achieve high quality terminal and software environments that enable free introduction of 3G applications and services. WHAT THE USER EXPECTS…….. Providing applications and content is key to the success of the 3G networks. These applications include video mail, video streaming, interactive gaming and high speed web browsing. The customer expects to be able to use these applications anytime and at any place in the 3G networks even while he is roaming. TESTING IN 3G NETWORKS In the 3G networks there needs to be interoperability between the application layer in the handset and the server. The application layer testing in the 3G networks can be divided into two steps Application Layer Testing and Application Delivery Testing Application layer testing In this phase we are looking to test the correct operation of the application in the handset and the correct interaction between the application processor in the handset and the server. Application delivery testing In this phase we look at how the application works in the dynamic networks , with radio propagation issues , network errors and changing radio bearer configurations. PROPOSED SOLUTIONS The current testing strategy are useful for testing on live networks where it is difficult to create faults in repeated and controlled manner. The test and measurement industry is now developing new types of system simulator environments that move beyond conformance tests and allows operators to quickly and easily test applications in many complex and demanding environments. Issue-3 IMPACT OF VOICE and DATA TRAFFIC The provision of multimedia services to mobile users is one of the main goals of 3G systems. The traffic transferred in the network will be composed by different information flows with various constraints on the required QoS. The issue over here is to decide whether to share a single frequency between different services or reserve different frequencies for different services. UMTS The UMTS terrestrial radio access network (UTRA) is devised to provide access to different services ranging from the classical speech service (8-12,Z Kb/s) to high rate packet data service (up to2 Mb/s). W-CDMA (Wideband CDMA) which adopts frequency division duplexing (FDD), and TD-CDMA (Time Division and Code Division Multiple Access) which is based on time division duplexing (TDD) The UMTS standardization bodies have designed a radio interface highly flexible able to provide different bearer services with different bit rates and different transfer modes Circuit switching and packet switching are the two transfer modes that are available In each transfer mode different quality of service can be achieved by suitably setting physical layer parameters such as the spreading factors (SF) of the physical channels, the rate of the FEC (Forward Error Correction) code used to protect information hits, the target SIR of the power control procedure 3G operators have to decide whether to reserve different frequency carriers to different services or to share a single frequency carrier between different services. When different services contend for the shared resource, their performance characteristics may highly change from the single service case. Transport channels are divided into dedicated channels, which can be assigned and then used only for transmissions to and from a single mobile terminal (MT) at a time, and common channels which are time shared by different MTs Speech traffic is transported over dedicated channels. Dedicated Channels (DCH) are assigned to single users through set-up and tear down procedures and are power controlled according to a closed loop mechanism that adjusts transmission power in order to keep the SIR (Signal to-Interference-Ratio) at a target value. Packet data can he delivered using a circuit oriented scheme which still adopts dedicated channels, or can be delivered using ad-hoc shared resources. In particular, two different shared channels are available for packet transmissions: DSCH (Downlink Shared Channel) and FACH (Forward Access Channel). DSCH users must have an associated active DCH on the downlink whose power control mechanism is also used to control the power of the shared channel itself. The FACH is shared by many users to transmit short bursts of data, but, unlike DSCH, no closed-loop power control is exerted and no DCH must he activated to access this channel. Experimental Setup The performance of the network is measured by using three parameters SIR (Signal to Interference Ratio) BLER (Block Error Rate , to measure quality of voice calls) Average packet delay and throughput are used to measure the data traffic performance. RESULTS OF VARIOUS SIMULATIONS All the results that are being presented were obtained using steady state simulations 900 seconds long. The first 100 seconds are used as warm up time , no data is collected during this time. The remaining 800 seconds are divided into four simulation runs and during each run the results are collected and used to evaluate one sample of each statistical data. Simulation conditions No Data in the network Only a number of voice calls are accepted If a too small SIR target is chosen too many errors occur since the code protection is useless. On the other side, with a high SIR target the power requirement increases and too many transmissions tend to be driven into saturation. We observe that for almost all the cases considered the SIR target value around 3 dB provides the lowest BLER. With such a SIR target value, up to 80 voice users per cell can be served with a BLER lower than 1%. SECOND SIMULATION 10 data users using 4 DSCH channels at a data rate of 100Kbps Results of the second simulation are Number of voice calls is reduced to 65 from 80 The SIR target value is 2dB higher than the value which provides lowest BLER in only voice calls scenario The interference has a higher standard deviation in the case of mixed traffic, therefore the power control cannot easily track interference variations and an higher value of SIR target is needed in order to prevent the SIR fluctuations from affecting the BLER of voice calls INTERFERENCE STANDARD DEVIATION vs NUMBER OF VOICE USERS The next figure shows the average packet delivery delay versus the throughput of one SF 4 DSCH shared by 10 data users, for several numbers of voice users active in the same cell. The performance of the downlink shared channel is obviously affected by the presence of voice calls interference, and drops dramatically if the number of voice users grows above 30. CONCLUSIONS OF THE EXPERIMENTS. The system capacity always decreases when mixing voice and data traffic in the network. Data transmissions can operate temporarily beyond full capacity even if the required power is not there , since they can take advantage of retransmissions Adding a certain load of data traffic requires to drop an higher load of voice traffic due to the increased burstiness of interference level. The interference generated by the voice calls limits the capacity of data service in terms of maximum throughput. 3G vs Wimax Wimax today UMTS TDD’s Quiet Path Hype UMTS TDD today 3G FDD today Gartner Hype Cycle TDD no-hype shortcut Time Will there really be any market opportunity left in 2009? “Enterprises should continue watching the technology but not consider short-term deployment” Gartner Research Brief, May 11 2004 references http://www.kerton.com/papers/Kerton_WCA_%20june2004.ppt#275,1 2,But Don’t Take My Word For It http://libproxy.library.unt.edu:2133/iel5/71/28460/01271183.pdf?tp=& arnumber=1271183&isnumber=28460 http://libproxy.library.unt.edu:2133/iel5/9803/30912/01434515.pdf?tp =&arnumber=1434515&isnumber=30912 http://libproxy.library.unt.edu:2133/iel5/9803/30912/01434450.pdf?tp =&arnumber=1434450&isnumber=30912