subject: The Design Architectural Planning to Optimization for Wireless Technologies [print this page] The Design Architectural Planning to Optimization for Wireless Technologies
The Design Architectural Planning to Optimization for Wireless Technologies
Dr.Hari Ramakrishna
Professor, Department of CSE,
Chaitanya Bharathi Institute of technology
Gandipet -500 075, Hyderabad,
dr.hariramakrishna@rediffmail.com
K.Ravi
Asst. Professor
Dept. of Informatics
Alluri Institute of Management Sciences
kolipakaravi@yahoo.co.in
ABSTRACT:
The fixed/portable broadband wireless access is becoming a necessity for many residential and business subscribers worldwide. The demand is exploding as the pricing of broadband services is rapidly decreasing. The worldwide interoperability for microwave access (WiMAX) technology is an integral part of the portfolio by complementing 3G/4G mobile access.
A WiMAX radio coverage simulation and analysis at different frequency bands for different demographic is presented. Furthermore, the WiMAX business models and a comparison with two enhanced third-generation (3G) technologies that are potential competitors to WiMAX are explored.
Keywords: WiMAX, Network Architecture, MIMO, IP, 1XEVDO, HSDPA/HSPA, WiFi, VoIP
1. INTRODUCTION
WiMAX will boost today's fragmented broadband wireless access market and mobile WiMAX promises to offer a solution to closing the existing digital divide. WiMAX can address the fixed wireless access and portable Internet market, complementing other broadband wireless technologies. Government initiatives to reduce the digital divide are making gains for broadband wireless countries such as Australia, South Korea, Taiwan, and the United States have programs in place today, and there has been a push by the European Commission for more flexible spectrum policies.
WiMAX access can be easily integrated within both fixed and mobile architectures, enabling operators to integrate it within a single converged core network, thereby providing new capabilities for a user-centric broadband world.
WiMAX addresses the following needs which may answer the question of closing the digital divide [1]:
Cost effective
Offers high data rates
Supports fixed, nomadic, and mobile applications thereby converging the fixed and mobile networks
Easy to deploy and has flexible network architectures
Supports interoperability with other networks
Aimed at being the first truly a global wireless broadband network
WiMAX is a standard that is championed by the WiMAX forum which was formed in June 2001
to promote conformance to IEEE 802.16 standard. The WiMAX forum currently has more than 470 members comprising the majority of operators, component, and equipment companies in the communications ecosystem. The WiMAX forum promotes interoperability by working closely with IEEE and other standards groups such as the European Telecommunications Standards Institute (ETSI) which have their own versions of broadband wireless. Along these lines, the WiMAX forum works closely with service providers and regulators to ensure that WiMAX forum certified systems meet customer and government requirements.
2. WIMAX NETWORK ARCHITECTURE
The mobile WiMAX end-to-end network architecture is based on an All-Internet Protocol (IP) platform, all packet technology, and no circuit switch telephony. The end-to-end architecture makes the greatest possible use of IETF and IEEE standards and protocols along with the adoption of commonly available standard equipment.
The open IP architecture gives network operators great flexibility when selecting solutions that work with legacy networks or that use the most advanced technologies, and in determining what functionality they want their network to support. They can choose from a vertically integrated vendor that provides a turnkey solution or they can pick and choose from a dense ecosystem of best-of-breed players with amore narrow focus. The architecture allows modularity and flexibility to accommodate a broad range of deployment options such as small scale to large scale, urban, suburban, and rural coverage, mesh topologies, flat, hierarchical and their variant, and finally, coexistences of fixed, nomadic portable and mobile usage models [4].
The WiMAX network supports the following key functions:
All-IP access and core service networks
Support for fixed, nomadic, and mobile access
Interoperability with existing networks via internetworking functions
Open interfaces between ASNs and between the ASN and the CSN
Support for differential quality of service (QoS) depending on the application
Unbundling of the access, core, and application service networks
FIGURE 1: WiMAX Network Architecture.
2.1 ACCESS SERVICESNETWORK
The ASN is the access network of WiMAX and it provides the interface between the user and the core service network. Mandatory functions as defined by the WiMAX forum include the following:
Handover
Authentication through the proxy authentication, authorization, and accounting (AAA) server
Radio resource management
Interoperability with other ASN's
Relay of functionality between CSN and mobile station (MS), e.g., IP address allocation
Base station (BS): The cell equipment comprises the basic BS equipment, radio equipment, and BS link to the backbone network. The BS is what actually provides the interface between the mobile user and the WiMAX network. The coverage radius of a typical BS in urban areas is around 500900m [6]. In rural areas the operators are planning cells with a radius of 4 km. This is quite a realistic number now and quite similar to the coverage areas of GSM and UMTS high-speed downlink packet access (HSDPA) BSs today.
Deployment is driven either by the bandwidth required to meet demand, or by the geographic coverage required to cover the area. Based on the cell planning of other previous technologies, urban and suburban segments cell deployment will likely be driven by capacity. Rural segment deployment will likely be driven by the cell radius. For BTS systems, the emphasis is more on performance than on cost and size, although there still is an interest in low cost because WiMAX is a new deployment.
2.2 CORE SERVICESNETWORK
The CSN is the transport, authentication, and switching part of the network. It represents the core network in WiMAX. It consists of the home agent (HA) and the AAA system and also contains the IP servers, gateways to other networks, i.e., public switched telephone network (PSTN), and 3G.
WiMAX has five main open interfaces which include reference points R1, R2, R3, R4, and R5 interface [7]. The R1 interface interconnects the subscriber to the BS in the ASN and is the air interface defined on the physical layer and Medium Access Control (MAC) sublayer. The R2 is the logical interface between the mobile subscriber and the CSN. It is associated with authorization, IP host configuration management, services management, and mobility management. The R3 is the interface between the ASN and CSN and supports AAA, policy enforcement, and mobility management capabilities. The R4 is an interface between two ASNs. It is mainly concerned with coordinating mobility of MSs between different ASNs. The R5 is an interface between two CSNs and is concerned with internetworking between two CSNs. It is through this interface that activities such as roaming are carried out.
3 TECHNOLOGIES EMPLOYED BY WiMAX
Mobile WiMAX operates in licensed frequency bands in the range of 2 to 6MHz. The technologies employed by mobile WiMAX include the following:
Scalable orthogonal frequency division multiple access (SOFDMA) on the physical layer
MIMO
IP
Adaptive antenna systems (AAS)
Adaptive modulation schemes (AMS)
Advanced encryption standard (AES) encryption
3.1 PHYSICAL LAYER
Mobile WiMAX will initially operate in the 2.3, 2.5, 3.3, and 3.43.8GHz spectrum bands [8] using SOFDMA. OFDMA is perhaps the most important technology associated with WiMAX. SOFDMA is based on OFDMA which in turn is based on OFDM [9]. OFDM is a form of frequency division multiplexing, but it has higher spectral efficiency and resistance to multi path fading and path loss compared to other multiplexing methods. It divides the allocated frequency spectrum into sub carriers which are at right angles to each other.
This reduces the possibility of cross-channel interference thereby allowing the sub carriers to overlap. This reduces the amount of frequency spectrum required, hence the high spectral efficiency. The reduced data rate of each stream reduces the possibility of inter symbol interference because there is more time between the arrival of symbols from different paths. This feature of OFDM makes it resistant to multi path fading and ideal for online of sight (NLOS) applications. In OFDMA each frequency sub carrier is divided into sub channels which can be accessed by multiple users hence increasing the capacity of OFDM [10].
3.2 MAC SUBLAYER
The 802.16 MAC sublayer uses a scheduling algorithm for which the subscriber station only needs to compete for initial entry into the network. The scheduling algorithm also allows the BS to control QoS parameters by balancing the time-slot assignments among the application needs of the subscriber stations.
WiMAX supports QoS differentiation for different types of applications. The 802.16 standard defines the following types of services [12]:
Unsolicited grant services (UGS): UGS is designed to support constant bit rate (CBR) services, such as T1/E1 emulation, and Voice-over-IP (VoIP) without silence suppression.
Real-time polling services (rtPS): rtPS is designed to support real-time services that generate variable size data packets on a periodic basis, such as MPEG video or VoIP with silence suppression.
Nonreal-time polling services (nrtPS): nrtPS is designed to support nonreal-time services that require variable size data grant burst types on a regular basis.
Best effort (BE) services: BE services are typically provided by the Internet today forWeb surfing.
4 NETWORK DIMENSIONING AND DESIGN
Designing, deploying, and managing any wireless cellular system requires clear objectives to be identified from the outset. These includes definition of the footprint coverage, the estimated number of users, the traffic load distribution, the penetration and growth rate, and inter network access and roaming. Mobile WiMAX, which will be deployed like 2G and 3G cellular networks, supports fractional frequency. Fractional frequency reuse takes advantage of the fact that mobile WiMAX user transmit on sub channels and does not occupy an entire channel such as in 3G.
The objective of the radio network dimensioning and design activity is to estimate the number of sites required to provide coverage and capacity for the targeted service areas and subscriber forecast. This process is based on many assumption such as uniform distribution of subscribers, homogenous morphology and ideal site location. The main inputs required for network dimensioning are site equipment-specific parameters, marketing-specific parameters, and licenses regulation and propagation models [13]. Figure 2 shows the flow chart of activities performed in network design and planning, starting from data collection of marketing and design requirement input and achieving the business model to provide a nominal site plan using a network simulation software.
FIGURE 2: THE CELL PLANNING PROCESS.
Mobile WiMAX is designed to complement existing 2G/3G access technologies with an "Always Best Connected" experience with voice and data connections. There is a large range of possible scenarios for the deployment of mobile WiMAX, but main four categories are [14]
Fixed and mobile operator with enhanced data for GSM evolution (EDGE)/3G who uses mobile WiMAX as a complementary extension for data services
Mobile only operator with EDGE/3G who uses mobile WiMAX as a complementary extension for data services
Fixed operator who uses mobile WiMAX to compete with 3G operators for data and voice services
New entrant who uses mobile WiMAX to move into mobile marketthreat to incumbent mobile operator.
5. COMPARISON WITH COMPETING TECHNOLOGIES
At some point current 2G and 3Gnetwork operators will migrate to a 4G network technology. Mobile WiMAX is likely to face competition from 3G and 4G technology enhancements. They include the code division multiple access (CDMA) variants CDMA2000 and wideband-CDMA (WCDMA) and their enhancements which are 1x evolution data optimized (1xEVDO) and HSDPA, respectively. Unlike in the early days of the CDMA vs. GSM competition, this higher generation competition will be quite different and fruitful because for these new generations networks; the applications are separated and do not depend on each other. 4G networks will go far beyond 2G and 3G by mainly improving three parameters:
Interface technology: 4G standards will make a radical change and will use OFDM [9]. The new modulation itself will not automatically bring an increase in speed but very much simplifies the following two enhancements: Channel bandwidth: 4G systems will use a bandwidth of up to 20MHz, i.e., the channel offers four times more bandwidth than channels of current systems. As 20MHz channels might not be available everywhere, most 4G systems will be scalable, e.g., in steps of 1.25 MHz. It can therefore be expected that 4G channel sizes will range from 5 to 20 MHz. MIMO: The idea of MIMO is to use the multi path phenomena. Although this behavior is often not desired, MIMO makes active use of it by using several antennas at the sender and receiver side, which allows the exchange of multiple data streams, each over a single individual wave front. Two or even four antennas are foreseen to be used in a device. How well this works is still to be determined in practice but it is likely that MIMO can increase throughput by a factor of two in urban environments.
Increasing channel size and using MIMO will increase throughput by about 810 times. Thus speeds of 40 Mbps per sector of a cell are thus possible. Using a commonly accepted evaluation methodology for 3G systems, mobile WiMAX has been simulated against the 3G enhancements.
These simulations have shown that
Mobile WiMAX peak data rates are up to 5x better than 3G+ technologies.
Mobile WiMAX spectral efficiency is 3x better than any 3G+ technology.
Lower equipment cost for WiMAX due to certified products (compare with WiFi).
WiMAX requires new infrastructure while high-speed packet access (HSPA) rides on UMTS.
Roughly the same coverage (average 5 km).
Roughly the same performance (average 2Mbps per user).
HSDPA launched in 2006 while HSUPA will come in 2008.
WiMAX standard set end of 2005 and first products in 2006.
HSPA has a higher acceptance with mobile operator.
5.1 1XEVDO
This standard is developed by the third generation partnership project 2 (3GPP2), the body responsible for CDMA and EVDO. 1xEVDO is an enhanced version of CDMA2000-1x. There are four versions that have been released, namely, Rev. 0, Rev. A, Rev. B, and Rev. C. 1xEVDO is a high-speed data only specification for 1.25MHz frequency division duplex (FDD) channels with a peak downlink (DL) data rate of 2.4 Mbps. Improvements to CDMA2000-1x in the 1xEVDO Rev. 0 specification include [9]:
DL channel is changed from code division multiplexing (CDM) to time division multiplexing (TDM) to allow full transmission power to a single user.
DL power control is replaced by closed-loop DL rate adaptation.
Adaptive modulation and coding (AMC).
HARQ.
Fast DL scheduling.
Soft handoff is replaced by a more bandwidth efficient "virtual" soft handoff.
1xEVDO Rev. 0, however, was designed to support only packet data services and not conversational services. In 1xEVDO Rev. A and EVDO Rev. C (also dubbed DORC), additional enhancements were added to the 1xEVDO specification. They include the following [8]:
DL: Smaller packet sizes, higher DL peak data rate (up to 3.1Mbps), and multiplexing packets from multiple users in the MAC layer.
Uplink (UL): Support of HARQ, AMC, higher peak rates of 1.8 Mbps, and smaller frame size
5.2 HSDPA/HSPA
The WCDMA specification was enhanced to create the high-speed downlink packet access (HSDPA) and then HSPA specifications. The enhancements in HSDPA include AMC, multi code operation, HARQ, higher DL peak rates (up to 14 Mbps), and decentralized architecture where scheduling functions are moved from the radio network controller (RNC) to Node-B, thus reducing latency and enabling fast scheduling.
HSPA adds enhancement to the UL of the WCDMA specifications. In Ref. [9] a quantitative comparison of mobile WiMAX, 1xEVDO, and HSPA system performance was conducted based on the commonly accepted 1xEVDV evaluation criterion. The mobile WiMAX system configuration was based on the WiMAX forum baseline minimum configuration. Table 1 illustrates a comparison of mobile WiMAX with 3G enhancements.
These technologies, i.e., EVDO, HSPDA, and mobile WiMAX have several performance enhancing features in common as follows:
AMC
HARQ
Fast scheduling
Bandwidth efficient handoff
Table 1 : Comparison of mobile WiMAX with 3g enhancements
5.3 WIFI
WiMAX is different from WiFi in many respects. The WiFi MAC layer uses contention access. This causes users to compete for data throughput to the access point. WiFi also has problems with distance, interference, and throughput and that is why triple play (voice, data, video) technologies cannot be hosted on traditional WiFi. In contrast, 802.16 uses a scheduling algorithm. This algorithm allows the user to only compete once for the access point.
This gives WiMAX inherent advantages in throughput, latency, spectral efficiency, and advanced antenna support. Companies developing radical innovations may adopt different stances not only based on the strategic interests of the company but also by taking into other considerations such as the market and its needs and requirements, as well as other products it may carry. When comparing WiFi and WiMAX, one is comparing their substitutability and complementary to existing technologies and how different companies have and will view them. WiMAX and WiFi can offer some potentially significant cost savings for mobile network operators by providing an alternate means to backhaul BS traffic from cell site to the BS controllers. Mobile network operators typically utilize some type of wired infrastructure that they must buy from an incumbent operator. A WiFi or WiMAX mesh can offer a much more cost-effective backhaul capability for BSs in metropolitan environments.
Using WiFi and WiMAX open broadband wireless standards and implementing mobile computing, governments and partners can quickly and cost-effectively deploy broadband to areas not currently served, with little or no disruption to existing infrastructures. Standards-compliant WLANs and proprietary WiFi mesh infrastructures are being installed rapidly and widely throughout the world. Standards-compliant WiMAX products can provide NLOS backhaul solutions for these local networks and WiMAX subscriber stations can currently provide Internet access to customers such as schools and other educational institutions and campuses.
The results of the comparison show that mobile WiMAX has better performance in all the areas listed above (where it shares performance-enhancing features with EVDO and HSDPA/HSPA). Furthermore, the technologies on which mobile WiMAX is based result in lower equipment complexity and simpler mobility management due to the all-IP core network.
They also provide mobile WiMAX systems with many other advantages over CDMA-based systems such as
Tolerance to multi path and self-interference
Scalable channel bandwidth
Orthogonal UL multiple access
Support for spectrally-efficient TDD
Frequency-selective scheduling
Table 2: Summary of WiMAX Applications
6. APPLICATIONS
The WiMAX standard has been developed to address a wide range of applications. Based on its technical attributes and service classes, WiMAX is suited to supporting a large number of usage scenarios. Table 12.3 address a wide range of applications
6.1 VOIP AND IP
Mobile WiMAX is an all-IP network. The use of OFDMA on the physical layer makes it capable of supporting IP applications. It is a wireless solution that not only offers competitive Internet access, but it can do the same for telephone service.
VoIP offers a wider range of voice services at reduced cost to subscribers and service providers alike. VoIP is expected to be one of the most popular WiMAX applications. Its value proposition is immediate to most users. Although WiMAX is not designed for switched cellular voice traffic as cellular technologies as are CDMA and WCDMA, it will provide full support for VoIP traffic because of QoS functionality and low latency. IPTV enables a WiMAX service provider to offer the same programming as cable or satellite TV service providers. IPTV, depending on compression algorithms requires at least 1 Mbps of bandwidth between the WiMAX BS and the subscriber. In addition to IPTV programming, the service provider can also offer a variety of video on demand (VoD) services. IPTV over WiMAX also enables the service provider to offer local programming as well as revenue generating local advertising.
7. BENEFITS OF WiMAX
The WiMAX solution reflects the general trend in the communications industry toward unified packet-based voice and data networks. Fundamental benefits of this transition are reduced operation cost, improved network optimization, and better management of changes. The followings are some of the benefits of WiMAX.
Wireless. By using a WiMAX system, companies/residents no longer have to rip up buildings or streets or lay down expensive cables.
High bandwidth: WiMAX can provide shared data rates of up to 70 Mbps. This is enough bandwidth to support more than 60 businesses at once with T1-type connectivity. It can also support over a thousand homes at 1-Mbps DSL-level connectivity. Also, there will be a reduction in latency for all WiMAX communications.
Long range. The most significant benefit of WiMAX compared to existing wireless technologies is the range. WiMAX has a communication range of up to 40 km
Multi-application: WiMAX uses the IP and is therefore capable of efficiently supporting all multimedia services from VoIP to high speed Internet and video transmission. It also supports a differentiated QoS enabling it to offer dynamic bandwidth allocation for different service types. WiMAX has the capacity to deliver services from households to small and medium enterprises, small office home office (SOHO), cybercafs, multimedia Tele-centers, schools and hospitals.
Flexible Architecture: WiMAX supports several systems architectures, including point-to-point, point-to-multipoint, and ubiquitous coverage.
High security: The security of WiMAX is state of the art. WiMAX supports advanced encryption standard triple data encryption standard. WiMAX also has built-in VLAN support, which provides protection for data that is being transmitted by different users on the same BS. Both variants use privacy key management (PKM) for authentication between BS and SS station. WiMAX offers strong security measures to thwart a wide variety of security threats.
QoS. WiMAX can be dynamically optimized for a mix of traffic that is being carried. Multilevel service. QoS is delivered generally based on the service-level agreement between the end user and the service provider.
Interoperability. WiMAX is based on international, vendor-neutral standard. This protects the early investment of an operator because it can select the equipments from different vendors.
Low cost and quick deployment. WiMAX requires little or no external plant construction compared with the deployment of wired solutions. BSs will cost under $20,000 but will still provide customers with T1-class connections [29].
Worldwide standardization. WiMAX is developed and supported by the WiMAX forum (more than 470 members). The WiMAX forum collaborates with different international standards organizations that are developing broadband wireless standards with the intent to provide interoperability among the standards. Some of the other broad band wireless standards include Hiper MAN/HiperLAN (Europe) and WiBRO (South Korea). These standards are compatible with WiMAX at the physical layer. WiMAX will become a truly global technology-based standard for broadband and will guaranty interoperability, reliability, and evolving technology and will ensure equipment with very low cost.
8. DRAWBACKS OF WiMAX
The most significant challenge is that WiMAX is a new technology with emerging support. Hesitancy. Companies are very hesitant of setting up WiMAX BSs today because it has not yet reached widespread use. Intel has made their Centrino laptop processors WiMAX enabled.
Exclusion of start-up companies. Even though cost provides a low barrier to entry, none of the start-up companies are projected to be major players in the development of WiMAX. Intel and Cisco seem to have an obvious advantage today, and by the time it reaches widespread use, large operators will find WiMAX to be a very attractive new way of raising revenues.
9. CONCLUSION
The combination of both advanced radio features and flexible end-to-end architecture makes WiMAX attractive solution for diverse operators. It provides many different services on one network, services which required different networks in the past. It also provides convergence of fixed and mobile networks. It provides high speed access to the subscriber at a reasonable cost, thereby enabling the service provider to make a profit from the technology, using economies of scale. It offers the advantage of reduced total cost of ownership during the lifetime of a network deployment. Standalone WiMAX networks are certainly feasible, but in most cases operators as an extension to their existing networks will adopt WiMAX access technology. This allows operators to make the most of their existing infrastructure such as BS sites, and IP service infrastructure for service and related AAA and billing systems.
In regard to WiMAX planning and cell design, the radio enhancement feature applicable to fixed and mobile WiMAX compensate for the extra attenuation resulting from higher carrier frequency, larger transmission bandwidth, and deep indoor penetration. WiMAX is expected to take prominence in about five years (2012).The strengths of WiMAX lie in its ability to address the requirements of modern telecommunications networks and the commitment that has been shown to its development and wide acceptance by a number of leading equipment vendors and service providers. The biggest challenges to deploying WiMAX-based services do not stem very much from the spectrum, but from business case issues.
10. REFERENCES
[1] G. Smyth, Wireless Technologies and e-learning: Bridging the digital divide, Intel Corporation, December 2006.
[2] G. Cayla, S. Cohen, and D. Guigon,WiMAX an efficient tool to bridge the digital divide,WiMAX Forum, November 2005, p. 2.
[3] S. Rahman and M. Pipattanasomporn, Alternate technologies for telecommunications and internet access in remote locations. In Proceedings of 2002 3rd Mediterranean Conference and Exhibition on Power Generation, Transmission, Distribution and Energy Conversion, Greece, November 2002.
[4] L. Bai, Analysis of the market for WiMAX services, Thesis, Lyngby, Denmark, May 2007.
[5] P. Yegani, Cisco Systems white paper,WiMAX Overview, IETF-64 November 711, Vancouver, Canada, 2005, p. 4.
[6] B. Puzzolante, G. Redaelli, andG.Grazia, Nationwide implementation of aWiMAXmobile access network at CEFRIEL, STEM, 2006.
[7] L. Nuaymi, WiMAX Technology for Broadband and Wireless Access, John Wiley, New York, 2007.
[8] M. Paolini, Mobile WiMAX: The best personal broadband experience! WiMAX forum, June 2006. pp. .
[9] Flarion, OFDM for mobile data communication, August 2004.
[10] G. Parsaee and A. Yarali,OFDMA for the 4th generation cellular networks, (CCECE 2004), Niagara Falls, Canada, May 25, 2004.
[11] A. Salvekar, S. Sumeet, L. Qinghua, V. Minh-Anh, and Q. Xiaoshu, Multiple-antenna technology in WiMAX systems, Intel Technology Journal, 8(3), 235, August 20, 2004.
[12] G. Nair, J. Chou, T. Madejski, K. Perycz, D. Putzolu, and J. Sydir, IEEE 802.16 medium access control and service provisioning, Intel Technology Journal, 8(3), 217, August 20, 2004.
[13] B. Upase, M. Hunukumbure, and S. Vadagana, Radio network dimensioning and planning for WiMAX networks, Fujitsu Sci. Tech. J. 43(4), 435450, October 2007.
[14] White paper, A comparative analysis of mobile WiMAX deployment alternatives in the access networks, WiMAX forum, May 2007.
[15] White Paper, IEEE 802.16a Standard and WiMAX igniting broadband wireless access, WiMAX forum, 2003.
