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3G Wireless Backhaul After several years of moderate growth, the wireless infrastructure market, which includes 3G and fixed broadband wireless, has begun to show strong signs of recovery. According to IDATE, investment is set to increase this year by more than 20% in NA and APAC, and by 6% in Europe. It is expected that the investment in 2G and 2.5G systems will continue at the same level between 2006 and 2009. However, it is also expected that the investment in W-CDMA equipment will increase by more than 40%, in contrast with a 30% decrease in CDMA2000. According to ABI Research, the key motivators for capital expenditures in the past were focused on customer acquisition to increase market share. Today, however, it seems to be that the key motivator is to increase ARPU and reduce costs associated with operating the backhaul network. The reason for the expected increase is mostly due to the fact that most GSM operators have started or committed to migrate towards 3G within the next few years. Similarly, service providers currently offering 3G services have also initiated the transition towards incorporating HSDPA/HSUPA, even though the transition from 2G is still underway. It is reasonable to assume that in the next few years 3G (i.e. UMTS) will overlap with 2G services, including GSM, GPRS and EDGE. In practice, this means that most GSM BTS and BSC network elements will be co-located, for the most part, with UMTS Node B and RNC network elements, including UMTS Release 99 and UMTS Release 4, 5 and 6. Initially, the majority of the traffic from these co-location sites could be safely assumed to be dominated by GSM voice traffic, requiring an average of two to three E1 links to connect the BTS to the aggregation network. In subsequent years, however, it is expected that UMTS and HSDPA will eventually become the dominant traffic at these sites, initially requiring an expansion in terms of capacity from the co-location site equivalent to two to four E1 links per Node B. With the migration towards 3G underway, GSM traffic from the BTS will continue to be transported over E1 links from the BTS, and transported over the backhaul network towards the BSC using conventional TDM transport (e.g. SDH). 3GPP Release 99, however, defines ATM as the bearer technology for UMTS's backhaul network used to aggregate and transport traffic from multiple Node B and RNC sites. It is expected that when service providers migrate towards HSDPA/HSUPA and begin introducing IMS (Release 6), and fixed-mobile converged services (Release 7), the connectivity between the Node B and the RNC will shift away from ATM in favor of IP. This will have a great impact on the backhaul network, especially considering that within a couple of years the traffic patterns will no longer be dominated by compressed voice services, but rather by multimedia interactive services. The introduction of W-CDMA as the UMTS air interface in Release 99, and the enhancements in both the downlink (HSDPA) and uplink (HSUPA) direction introduced in Releases 5 and 6 respectively, will effectively enable service providers to offer new advanced IP services such as mobile TV and on-demand multimedia, as well as peer-to-peer applications such as file sharing, and point-to-point and multipoint communication such as VoIP and video conferencing over the air interface. While this will represent a clear business opportunity for wireless service providers, it also represents a challenge given the need for immediate investment in the backhaul network in order to meet the projected customer demand for these services. This will be further accelerated by the rapid development of WiFi and WiMax standards, that will eventually enable users to roam between mobile and fixed wireless networks, effectively demanding fixed-mobile converged services. IMS and fixed-mobile convergence will introduce new traffic behaviors and will demand higher data rates. This, in combination with a rapid increase in customer density and coverage area, will present service providers with the following challenges:
Currently, most service providers rely on a series of point to point TDM links to interconnect the 2G BTS and the BSC. However, this design cannot scale to satisfy the demands for 3G services or the introduction of new multimedia services (MMS) defined in Release 99 even when the migration from GSM/GPRS is not directly to UMTS, but executed gradually by introducing EDGE technology prior to UMTS. The RAN design for GSM and GPRS therefore assumes the vast majority of traffic to be compressed voice rather than derived from data services, which are assume to be limited and not having any impact on the capacity requirements for the RAN. Network engineering is therefore done based on the expected customer density and average voice usage, leading in most cases towards a network design in which a low capacity backhaul network, mostly based on a reduced number of point to point E1 links, is sufficient to satisfy the capacity requirements for the backhaul network.
The 2G backhaul network design, however, cannot scale to meet the needs of a dramatic increase in customer demand and the introduction of a new air interface based on W-CDMA. Service providers currently migrating or looking into migrating to 3G as defined in Release 99, may do so by migrating first to EDGE or directly to UMTS. EDGE introduces the ability to increase the data-rate over the air interface to up to 384 kbits/s, however no changes are introduced in the GERAN. However, the introduction of the UTRAN also introduces new network elements and a new interface between them based on ATM.
3G service providers may decide also to migrate towards HSDPA/HSUPA and adopt 3GPP Release 4 split-architecture or implement an all-IP backhaul network as defined in Release 5. This will mean the interfaces from the Node B and RNC will be based on IP/Ethernet or IP/MPLS/Ethernet, effectively introducing native IP-based equipment for the UTRAN.
It is evident that service providers looking to migrate towards 3G services, including UMTS and HSDPA/HSUPA, require a strategy that will allow them to accelerate the development of new revenue-generating 3G services in the hope of increasing the 3G services ARPU and maximize the return on investment. This strategy, however, cannot be based on building multiple parallel networks or technology overlays as it will imply a prohibitive increase in OPEX, added to the necessary expense associated with the air interface and new UTRAN. Therefore, in order to figure out the right network architecture to invest in, service providers need to consider the following aspects:
Corrigent Systems believes that the ideal solution to provide cost-effective transport and aggregation of multiple generations of wireless technologies and services, is through a high-capacity, packet-based mobile backhaul network, capable of providing bandwidth efficient transport of legacy 2G (TDM), existing 3G (ATM) and future 4G (IP) services. Corrigent's Packet Transport for the Radio Access Network Corrigent's packet transport solution, allows service providers to secure their investment in 2.5G and 3G infrastructure, by cost-effectively scaling from pure TDM/ATM services to predominantly 3G data services. This will also enable service providers to expand network capacity as needed without the risk of spending on surplus network capacity.
Specifically, Corrigent offers the most efficient packet transport solution and the only one capable of providing a converged solution for TDM, ATM and Ethernet, effectively consolidating services and transport technologies into a single efficient packet transport platform. Implicitly, Corrigent's approach also provides an alternative to reduce OPEX by also eliminating the multiple parallel networks or network overlays normally required by service providers migrating from 2G to 3G (UMTS and HSDPA) services. Corrigent's solution also allows service providers to make the most efficient use of the backhaul network resources, by enabling the statistical multiplexing of GSM, UMTS and HSDPA traffic over a single RPR shared media. The benefits of statistical multiplexing in a packet efficient network infrastructure, permits service providers to begin offering new revenue generating 3G services, towards increasing the ARPU and as a result maximize the return on investment. Corrigent offers a future-proof network solution to wireless operators wanting to gradually migrate from GSM to 3G services, and to those looking either today or tomorrow to migrate to HSDPA and towards offering fixed-mobile converged services. It offers a packet transport solution capable of scaling in capacity according to the customer needs, and offering a cost-effective migration path towards 3G and beyond. Specifically, Corrigent's packet transport solution can represent a cost reduction in terms of initial investment as well as OPEX. However, the greater value derived from Corrigent's packet transport solution is through time, as it provides the lowest incremental cost over time, effectively extending the amortization period for the backhaul network. With Corrigent's packet transport solution, not only high-availability and scalability are guaranteed, but also the performance of every application including compressed voice, mobile TV and VoIP. This is achieved by using MPLS pseudowire and RPR traffic management, which allow the universal encapsulation (packetization) and statistical multiplexing of 2G and 3G services. Specifically, RPR provides class of service differentiation and traffic management schemes that guarantees the performance of TDM, ATM and Ethernet traffic, consistent with the application requirements, including voice and data.
The CM-100 PTS can be deployed as part of the access or transport networks; however Corrigent's packet transport solution provides greater benefits when deployed as part of the transport network (Tier 2 aggregation) of the RAN/UTRAN, in which the level of aggregation of hundreds of BTS/Node B stations enables the most efficient use of the packet transport network. The figure below shows Corrigent can provide the desired connectivity for GSM, UMTS and HSDPA services, and how Corrigent can be used to provide reliable transport of 2G and 3G services towards the BTS and RNC nodes.
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