450 Part 4: Configuring Wireless High-Speed Data Networks almost ready to operate. The RMM will determine the correct tim- ing and synchronization in order to start running the newly creat- ed BPC object: BPC_id.resume() 5. Once the RMM has established an appropriate time and synchro- nization, it will put the new BPC object in Running state, wherein wireless data is processed as intended: BPC_id.run() Now, consider that this BPC object is to be reconfigured by chang- ing the process function within it. In other words, the functionali- ty of the convolutional encoder needs changing without destroying the BPC object. Such reconfigurations are typical of the type that is called partial reconfiguration for such instances. 6. The RMM will make a pointer reference (copy) of the BPC object in the shadow chain (*BPC_id). It will then put *BPC_id in a Sus- pended state: *BPC_id.suspend() 7. The RMM will reset the BPC object by instantiating a new process function. The new process function implies that there is no change in the input/output ports of *BPC_id, but simply a change in the resident wireless data processing entity process: *BPC_id.reset(new convolutionalEncoder (k 2 , G 2 (p))) where k 2 , G 2 ( p) are the new attributes of the process. 8. Once the BPC object has been reset, the RMM will then put it in Initialized state (step 4). The RMM will next issue the start signal to commence the newly configured BPC object in the shadow chain. Once that is done, it will then put the BPC object in Run- ning state by issuing the run signal (step 5). Now consider that a new type of FEC encoder is required and that the incumbent BPC object is to be replaced by a new BPC object with new input/out- put ports and a new process within it. Such reconfigurations are typical of the type called total reconfiguration for such instances: 9. The RMM will suspend the BPC object in the shadow chain (step 6). 10. The RMM will then remove this shadow BPC object by issuing a kill signal. The kill signal to the BPC object will destroy only the Chapter 18: Configuring Wireless Data process function within it. Once that is successfully completed, the RMM will delete the BPC object completely: BPC_id.KILL(), and then, delete BPC_id 11. The RMM will replace the killed BPC object with a new one in the shadow chain, which it created in the background following steps 1 to 5. 1 Reconfiguration Steps Finally, the following is a sequential list of steps that explain how baseband reconfiguration is managed and administered: 1. The RMM accepts a reconfiguration request from the terminal’s management entity, that is, a terminal management module (TMM). The request includes information on: Which BPC objects to reconfigure How to reconfigure them New configuration map Run-time signaling changes 2. RMM then negotiates the reconfiguration request with the TMM. This includes details such as: Complexity of reconfiguration Processing and memory requirements Time duration for reconfiguration 3. RMM will perform an RF capability check by referring to the RF property list. 4. Following a successful negotiation, the TMM will instruct the RMM with: A list of BPCs to be reconfigured How to reconfigure them When to reconfigure them 5. As part of the successful negotiation, the RMM instructs the TMM if new software needs to be downloaded, or whether it intends to use the already present software from its local library store. 6. The TMM then instructs the software download module (SDM) if new software needs to be acquired and then instructs the RMM when it is available. 7. RMM reads the necessary software from the baseband software library. This could be either the newly downloaded code or that already present. 451 452 Part 4: Configuring Wireless High-Speed Data Networks 8. RMM then creates the shadow transceiver chain. The shadow chain contains the new baseband modules and pointer references of the unchanged modules, which are intended to remain from the current baseband chain. 9. RMM then validates the shadow chain such that it complies with the agreed configuration map in terms of interfaces between neighboring BPC objects and their input/output ports. 10. Once the RMM has successfully configured the shadow chain, it will then instruct the RF subsystem to retune its filters. 11. While the RF subsystem is being reconfigured, the RMM will reconfigure the chosen BPC objects in accordance with the STD. 12. The RF subsystem will send an acknowledgment back to the RMM after it has successfully reconfigured. Then the RMM is in a position to switch the shadow BPC object on and thus complete a given baseband reconfiguration. 1 The switch-over between shadow and active chains needs to be autho- rized by the TMM in order to maintain network compliance. Conclusion The realization of a reconfigurable user terminal based on wireless data software-defined radio technology demands novel architectural solutions and conceptual designs, both from a terminal-centric viewpoint and also with regard to provisions in the host networks. Following investigations in the TRUST project, it is clear that in order to develop a terminal that is able to reconfigure itself across different radio access standards, there need to be some supporting mechanisms within the different wireless data networks. Considering these aspects together with the technical solutions needed, the TRUST project has proposed several entities needed to enable terminal reconfiguration. This chapter presented architectural solutions for the following aspects, identified in the TRUST project: Mode identification Mode switching Software download Adaptive baseband processing Finally, these solutions provide insight into the type of entities neces- sary to develop a feasible RUT based on SDR technology. In addition, it also helps you to understand the framework (wireless data network and Chapter 18: Configuring Wireless Data terminal entities and flexible processing environment) needed for adapt- ing terminal functionality, behavior, and mode (radio access technology) in accordance with user requirements, terminal capability, and available services across detected modes. The added benefit of such a flexible solu- tion will help yield improved QoS to the user, multimode capability, and adaptive pricing and service packaging. References 1. Mehul Mehta, Nigel Drew, Georgios Vardoulias, Nicola Greco, and Christoph Niedermeier, “Reconfigurable Terminals: An Overview of Architectural Solutions,” IEEE Communications Magazine, 445 Hoes Lane, Piscataway, NJ 08855, 2002. 2. John R. Vacca, i-mode Crash Course, McGraw-Hill, 2001. 453 This page intentionally left blank. Configuring Broadband Wireless Data Networks 19 CHAPTER 19 Copyright 2003 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use. 456 Part 4: Configuring Wireless High-Speed Data Networks The wireless data communications industry is gaining momentum in both fixed and mobile applications. 2 The continued increase in demand for all types of wireless data services (voice, data, and multimedia) is fueling the need for higher capacity and data rates. Although improved compression technologies have cut the bandwidth needed for voice calls, data traffic will demand much more bandwidth as new services come on line. In this context, emerging technologies that improve wireless data systems’ spectrum efficiency are becoming a necessity, especially in the configuration of wireless data broadband applications. Some popular examples include smart antennas, in particular multiple-input, multiple- output (MIMO) technology; coded multicarrier modulation; link-level retransmission; and adaptive modulation and coding techniques. Popularized by cellular wireless data standards such as Enhanced Data GSM Evolution (EDGE), adaptive modulation and coding tech- niques that can track time-varying characteristics of wireless data chan- nels carry the promise of significantly increasing data rates, reliability, and spectrum efficiency of future wireless data-centric networks. The set of algorithms and protocols governing adaptive modulation and cod- ing is often referred to as link adaptation (LA). While substantial progress has been accomplished in this area to understand the theoretical aspects of time adaptation in LA protocols, more challenges surface as dynamic transmission techniques must take into account the additional signaling dimensions explored in future broad- band wireless data networks. More specifically, the growing popularity of both multiple transmit antenna systems [MIMO and multiple-input, single- output (MISO)] and multicarrier systems such as orthogonal frequency- division multiplexing (OFDM) creates the need for LA solutions that integrate temporal, spatial, and spectral components together. The key issue is the design of robust low-complexity and cost-effective solutions for these future wireless data networks. This chapter is organized as follows. First, the traditional LA tech- niques are introduced. Then other emerging approaches for increasing the spectral efficiency in wireless data access systems with an emphasis on interactions with the LA layer design are discussed. Next, the chap- ter focuses on smart antenna techniques and coded multicarrier modu- lations. The chapter then continues with a short overview of space-time configuration broadband wireless data propagation characteristics. Then the chapter explores various ways of capturing channel informa- tion and provides some guidelines for the design of sensible solutions for LA. Finally, the chapter emphasizes the practical limitations involved in the application of LA algorithms and gives examples of practical perfor- mance. (The Glossary defines many technical terms, abbreviations, and acronyms used in the book.) Scheme Modulation Maximum Rate, kbps Code Rate MCS-9 8 PSK 59.2 1 MCS-8 54.5 0.92 MCS-7 44.8 0.76 MCS-6 29.6 0.49 MCS-5 22.4 0.37 MCS-4 GMSK 17.6 1 MCS-3 14.8 0.80 MCS-2 11.2 0.66 MCS-1 8.8 0.53 TABLE 19-1 EGPRS Modulation and Coding Schemes and Peak Data Rates Chapter 19: Configuring Broadband Wireless Data Networks Link Adaptation Fundamentals The basic idea behind LA techniques is to adapt the transmission parame- ters to take advantage of prevailing channel conditions. The fundamental parameters to be adapted include modulation and coding levels, but other quantities can be adjusted for the benefit of the systems such as power levels (as in power control), spreading factors, signaling bandwidth, and more. LA is now widely recognized as a key solution to increase the spec- tral efficiency of wireless data systems. An important indication of the popularity of such techniques is the current proposals for third-generation wireless packet data services, such as code-division multiple-access (CDMA) schemes like cdma2000 and wideband CDMA (W-CDMA) and General Packet Radio System (GPRS, GPRS-136), including LA as a means to provide a higher data rate. The principle of LA is simple. It aims to exploit the variations of the wireless data channel (over time, frequency, and/or space) by dynamically adjusting certain key transmission parameters to the changing environ- mental and interference conditions observed between the base station and the subscriber. In practical implementations, the values for the transmis- sion parameters are quantized and grouped together in what is referred to as a set of modes. An example of such a set of modes, where each mode is limited to a specific combination of modulation level and coding rate, is illustrated in Table 19-1. 1 Since each mode has a different wireless data rate (expressed in bits per second) and robustness level [minimum signal- to-noise ratio (S/N) needed to activate the mode], they are optimal for use 457 458 Part 4: Configuring Wireless High-Speed Data Networks in different channel/link quality regions. The goal of an LA algorithm is to ensure that the most efficient mode is always used, over varying channel conditions, based on a mode selection criterion (maximum data rate, mini- mum transmit power, etc). Making modes available that enable communi- cation even in poor channel conditions renders the system robust. Under good channel conditions, spectrally efficient modes are alternatively used to increase throughput. In contrast, systems with no LA protocol are con- strained to use a single mode that is often designed to maintain acceptable performance when the channel quality is poor to get maximum coverage. In other words, these systems are effectively designed for the worst-case chan- nel conditions, resulting in insufficient utilization of the full channel capacity. The capacity improvement offered by LA over nonadaptive systems can be remarkable, as illustrated by Fig. 19-1. 1 This figure represents the link-level spectral efficiency (SE) performance (bits per second per hertz) versus the short-term average S/N ⌼ in decibels, for four different uncoded modulation levels referred to as binary phase-shift keying (BPSK), qua- ternary PSK (QPSK), 16 quadrature amplitude modulation (QAM), and 64 QAM. The SE was obtained for each modulation by taking into account the corresponding maximum data rate and packet error rate (PER), which is a function of the short-term average S/N. The SE curve of two systems is highlighted. The first system is nonadaptive and con- strained to use the BPSK modulation only. Its corresponding SE versus S/N is represented by the BPSK modulation curve that extends from the intersection of SE 1y (bps) and S/N 10x (dB) straight across to the inter- section of SE 1y and S/N 30x. The second system uses adaptive modula- tion. Its corresponding SE is given by the envelope formed by the BPSK, QPSK, 16 QAM, and 64 QAM curves that extend from the intersection of SE 0y and S/N 0x to the intersection of SE 1y and S/N 10x, to the inter- section of SE 2y and S/N 17x, to the intersection of SE 4y and S/N 24x, and to the intersection of SE 6y and S/N 30x, respectively. It is seen that each modulation is optimal for use in different quality regions, and LA selects the modulation with the highest SE for each link. The perfor- mance of the two systems is equal for S/N up to 10 dB. However, in the range of higher S/N, the SE of the adaptive system is up to 6 times that of the nonadaptive system. When averaging the SE over the S/N range for a typical power-limited cellular scenario, the adaptive system is seen to provide a close to threefold gain over the nonadaptive system. The example in Fig. 19-1 is ideal since it assumes that the modula- tion level is perfectly adapted to the short-term average S/N, and that the probability of error as a function of the S/N is exactly known; for example, here an additive white gaussian noise (AWGN) channel is con- sidered, which corresponds to an instantaneous channel measurement. That assumption is true only for instantaneous feedback and is not practical because of delays in the feedback path. When there is delay, as Chapter 19: Configuring Broadband Wireless Data Networks explained later, the first- and higher-order statistics of the fading chan- nel should be incorporated to improve the adaptation. Furthermore, other dimensions such as frequency and space (where different trans- mission schemes may be adapted) may yield further gains simply by providing additional degrees of freedom exploitable by LA. Expanding the Dimensions of Link Adaptation “Smart antenna” technology is widely recognized as a promising tech- nique to increase the spectrum efficiency of wireless data networks. Sys- tems that exploit smart antennas usually have an array of multiple antennas at only one end of the communication link [at the transmit side, as in MISO systems, or at the receive side, in single-input, multiple- output (SIMO) systems]. A more recent idea, however, is multiarray or MIMO communication where an antenna array is used at both the transmitter and receiver. The potential of MIMO systems goes far beyond that of conventional smart antennas and can lead to dramatic increases in the capacity of certain wireless data links. In the so-called BLAST scenario, each antenna transmits an independently modulated sig- nal simultaneously and on the same carrier frequency. Alternatively, the 459 0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 Spectral efficiency (bps/Hz) S/N ⌼ (dB) 64 QAM 16 QAM QPSK BPSK Figure 19-1 Spectral efficiency for various modula- tion levels as a func- tion of short-term average S/N. [...]... Networks Copyright 2003 by The McGraw- Hill Companies, Inc Click Here for Terms of Use 472 Part 4: Configuring Wireless High-Speed Data Networks Configuring wireless data connectivity has implications for the specific mobile computing hardware you choose.2 While all types of devices support at least some types of wireless data connectivity, the specific type of wireless data network you configure will... Crash Course, McGraw- Hill, 2002 This page intentionally left blank CHAPTER 21 Configuring Residential Wireless Data Access Technology Copyright 2003 by The McGraw- Hill Companies, Inc Click Here for Terms of Use 480 Part 4: Configuring Wireless High-Speed Data Networks The meaning of residential (home) networking configuration is changing as a result of the introduction of new wireless data access... broadband wireless data MIMO-OFDM-based system using LA is very encouraging References 1 Severine Catreux, Vinko Erceg, David Gesbert, and Robert W Heath, Jr., “Adaptive Modulation and MIMO Coding for Broadband Wireless Data Networks,” IEEE Communications Magazine, 445 Hoes Lane, Piscataway, NJ 08855, 2002 2 John R Vacca, i-mode Crash Course, McGraw- Hill, 2001 CHAPTER 20 Configuring Wireless Data Mobile... and data service to users But this same, inexpensive, ubiquitous wiring, in combination with wireless data access technology, can also be used to network a home’s printer and entertainment devices and to add a new level to home security By simply installing this twisted pair wiring, in combination with wireless data access to all rooms in the home, you can virtually provide any type of wireless data. .. Wireless Data Access Technology 483 will be on line by 2006, with at least 76 percent of that group using multiple devices Wireless data home networking enables all devices (PCs, stereos, household appliances, TVs, printers, PDAs, electronic games, etc.) to operate together, sharing data over one unanimous information source By enabling these devices to communicate, users can perform the wireless data. .. converges toward the lower bound In general, it is seen that a twofold capacity gain may be achieved between the slowest and fastest adaptation rates 4 69 Chapter 19: Configuring Broadband Wireless Data Networks 2 1 .9 Spectral efficiency (bps/Hz) Figure 19- 6 Spectral efficiency versus normalized adaptation window, for various adaptation rates at fixed long-term average S/N Instantaneous LA Provisioned... techniques for increasing spectral efficiency in wireless data broadband access systems were presented; smart antenna techniques and coded multicarrier modulations, and their interactions 470 Part 4: Configuring Wireless High-Speed Data Networks with the LA layer design and configuration, were emphasized Following a short overview of space-time broadband wireless data propagation characteristics, the chapter... their television sets Wireless security features can also be accessed from outside of the home, via the Internet While away, parents can use features such as the wireless baby camera to check up on their child and the baby sitter, making sure that everything is going well Market Outlook The future of wireless data access home networking technology is strong (see sidebar, Wireless Data Access Residential... Ericsson, Siemens 473 Chapter 20: Configuring Wireless Data Mobile Networks helds Table 20-2 summarizes this information for the most popular hand-helds.1 Smart phones, WAP phones, and SMS phones all offer inherent network connectivity if they operate by digital technology The wireless data service provider the phone is configured for must also offer wireless data Internet service TABLE 20-2 Hand-Helds... also can utilize the wireless data network to enable the printer in the office to print documents stored on the computer in the bedroom, while the bedroom PC is supplying the MP3 files that are played on the stereo downstairs Tomorrow’s Wireless Data Home Networking Solution At the convergence of these trends, there is a clear demand within the technology industry for a wireless data home networking . i-mode Crash Course, McGraw- Hill, 2001. 453 This page intentionally left blank. Configuring Broadband Wireless Data Networks 19 CHAPTER 19 Copyright 2003 by The McGraw- Hill Companies, Inc Rate, kbps Code Rate MCS -9 8 PSK 59. 2 1 MCS-8 54.5 0 .92 MCS-7 44.8 0.76 MCS-6 29. 6 0. 49 MCS-5 22.4 0.37 MCS-4 GMSK 17.6 1 MCS-3 14.8 0.80 MCS-2 11.2 0.66 MCS-1 8.8 0.53 TABLE 19- 1 EGPRS Modulation and. by cellular wireless data standards such as Enhanced Data GSM Evolution (EDGE), adaptive modulation and coding tech- niques that can track time-varying characteristics of wireless data chan- nels