Pseudo-Wire: The Solution for HSDPA Offload WHITE PAPER

Transcription

1 Pseudo-Wire: The Solution for HSDPA Offload WHITE PAPER

2 Important Notice This document is delivered subject to the following conditions and restrictions: This document contains proprietary information belonging to Axerra Networks, Inc. Such information is supplied solely for the purpose of evaluating AXN Pseudo-Wire Gateways and Access Devices. Axerra Networks owns the proprietary rights to all information contained herein. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, magnetic, photocopy, recording, or otherwise, now or in the future, without prior written consent from Axerra Networks. The text and graphics are for illustration and reference only. The specifications on which they are based are subject to change without notice. Due to a policy of continuous development, Axerra Networks reserves the right to alter specifications and descriptions outlined in this publication without prior notice, and no part of this publication, taken separately or as a whole, shall be deemed to be part of any contract. Copyright Axerra Networks, Inc. Axerra, Axerra Networks, AXN, HPCR, AXN Pseudo-Wire Gateways and Access Devices, AXNVision, and The Pseudo-Wire Company are trademarks or registered trademarks of Axerra Networks, Inc. All other product names are trademarks or registered trademarks of their respective owners. - Page 2 of 8 -

3 Executive Summary Mobile operators are already using HSDPA capability to promote new high-value mobile services in both the business and consumer markets, with hopes of being ready for the widespread adoption of true mobile broadband data. It is essential that widespread adoption include enhancements in the RAN, where more bandwidth is required to effectively support the speeds of HSDPA services. Until the advent of HSDPA, operators have had the luxury of providing services with relatively low bandwidth requirements in the RAN. However, operators are marketing HSDPA with aggressive performance metrics in response to expected threats such as WiMAX. In order to meet customer expectations and provide a high-quality user experience, it is critical that HSDPA furnish the bandwidths advertised even as the number of subscribers grows. Operators acknowledge that HSDPA threatens to increase bandwidth requirements in the RAN by 2x, 4x, or more. To meet the requirement for increased bandwidth while simultaneously keeping the cost of HSDPA economically viable, the logical first step is to offload the HSDPA traffic onto a packet network. Separating the HSDPA traffic from the voice traffic, continuing to use lease-line E1s to backhaul voice and using a low-cost packet transport, such as DSL, to backhaul bursty HSDPA traffic makes sense. Pseudo-Wire technology is the logical solution for matching HSDPA traffic to ADSL backhaul. In its broadest sense, Pseudo-Wire includes service emulation for transport of frame-based and cell-based services over MPLS, IP, and Ethernet networks. Because HSDPA uses ATM cells and ADSL modems use an Ethernet connection, Axerra s Pseudo-Wire solution is a perfect interconnect technology. Axerra s Pseudo-Wire solution can be deployed today to offload HSDPA traffic using ADSL, but it can also enable backhaul over newer, higher-capacity transports and support true convergence of every generation of voice and data mobile service. New generations of services, including HSUPA and beyond (such as VDSL, copper bonding using Ethernet in the First Mile, and Carrier Ethernet over optical fiber), that offer ever greater speeds, especially in the upstream direction, are already on the horizon. In fact, Axerra s Pseudo-Wire solution is ready today to carry multiple generations of mobile services -- both voice and data -- over a single converged RAN. Axerra s Pseudo-Wire solution uniquely combines circuit emulation and service emulation (TDM plus HDLC, Frame Relay, and the ATM needed for 3G UMTS and HSDPA) to enable backhaul of any combination of 2G, 2.5G, and 3G voice and data traffic, as well as subscriber Ethernet interfaces for 4G traffic backhauling, all over a single packet RAN. Axerra s full-service Pseudo-Wire solution enables all generations of both voice and data over Carrier Ethernet, enabling mobile wireless providers to realize the true promise of convergence in the RAN and immediately profit from significant OpEx savings. ## - Page 3 of 8 -

4 Challenge Momentum behind HSDPA capability is gathering speed. Mobile operators are already using it to promote new high-value mobile services in both the business and consumer markets, with hopes of being ready for the widespread adoption of true broadband mobile data. However, to ensure the economic success of HSDPA, it is essential that preparations for widespread adoption include enhancements in the RAN, not just the air link spectrum. In the RAN, more bandwidth is required to effectively support the speeds of HSDPA services. Until the advent of HSDPA, operators have had the luxury of providing services with relatively low bandwidth requirements in the RAN. Today, many operators backhaul requirements from a single cell site often amount to only one E1; in some cases this even includes both 2G service and 3G service (R99 version). However, operators are marketing HSDPA with aggressive performance metrics in response to expected threats such as WiMAX. These marketing efforts should be viewed against a backdrop where ARPU and customer churn continue to challenge mobile operators business models. In order to meet customer expectations and provide a high quality user experience, it is critical that HSDPA furnish the bandwidths advertised even as the number of subscribers grows. Thus, operators acknowledge that HSDPA threatens to increase bandwidth requirements in the RAN by 2x, 4x, or more. According to promotional material for an Unstrung Insider report titled Wireless Backhaul & 3G Network Economics, 80 percent of cell sites will require the equivalent of between 4 and 8 E1s of capacity, with the remaining 20 percent requiring even greater capacity. To achieve these capacities while simultaneously keeping the cost of HSDPA economically viable, operators openly admit the cost per bit absolutely must be reduced compared to today s leased-line E1 backhaul. HSDPA Offload Using ADSL To meet the requirement for increased bandwidth with lower cost per bit, the logical first step is to offload the HSDPA traffic onto a packet network. HSDPA represents the data portion of a best-effort mobile service: the service is asymmetric in nature, user traffic tends to have bursty characteristics, and expectations are satisfied with non-continuous, brief utilization of the network bandwidth. This is quite different from the nature and expectations for voice traffic, which tends to have a more continuous rate, and where a continuous, reliable connection is essential even if the traffic is formed in packets or cells. Thus, separating the HSDPA traffic from the voice traffic, continuing to use leased-line E1s to backhaul the voice and using a lowcost packet transport to backhaul the bursty HSDPA traffic makes sense. DSL is a logical choice for the packet transport. It is a mature technology that has been widely deployed for residential and business data traffic. DSL enjoys the economies of scale of a mainstream data technology, with low-cost DSL modems readily available using the ubiquitous Ethernet interface to connect with users data traffic. xdsl furnishes the advantages inherent to packet transport, including statistical sharing of bandwidth among multiple users that is ideally matched to HSDPA needs. Wireless Backhaul & 3G Network Economics predicts that next-gen DSL has the most potential for cellular backhaul, and is likely to be used initially for data-only traffic in hybrid backhaul architectures. In particular, ADSL2 and ADSL2+ provide the speed and asymmetry that match HSDPA while retaining the cost and availability advantages. Plus, Carrier Ethernet is emerging as the next-generation technology for backhaul of ADSL2 traffic. A new generation of Ethernet DSLAMs has come to market that enables ADSL2 and ADSL2+ backhaul over Carrier Ethernet. - Page 4 of 8 -

5 Pseudo-Wire: The Solution for HSDPA and ADSL As much as ADSL is the first logical step for offload of HSDPA traffic, Pseudo-Wire technology is the logical solution for matching HSDPA traffic to ADSL backhaul. The term Pseudo-Wire comes from the IETF s Pseudo Wire Emulation Edge-to-Edge (PWE3) working group, which has defined various types of Pseudo-Wires to emulate a wide range of both traditional and emerging services over packet networks. In its broadest sense, Pseudo-Wire includes service emulation for transport of frame-based and cell based services over MPLS, IP, and Ethernet networks. Because HSDPA uses ATM cells and ADSL modems use an Ethernet connection, Axerra s Pseudo-Wire solution is a perfect interconnect technology. This figure shows a typical Axerra Pseudo-Wire deployment in the RAN using both access devices and gateways. Axerra s AXN1 and AXN10 Pseudo-Wire Access Devices, available with 1, 2, 4, or 8 E1 ports, are deployed at the cell sites where they connect to the existing NodeB equipment. In this application, the AXN access devices offer unique E1 interfaces that can be configured to perform ATM service emulation recognizing the native ATM cells used for HSDPA service and even terminating the IMA protocol from the NodeB. The result HSDPA service from multiple E1s is aggregated onto a single, efficient Pseudo-Wire and delivered to the ADSL modem on a single Ethernet connection. The ADSL traffic is backhauled to the mobile operator s RNC location using either an ATM network or, increasingly so, a Carrier Ethernet metro network. An AXN1600 or AXN800 Pseudo-Wire Gateway is deployed at the RNC, where it terminates the ATM Pseudo-Wire services and functions as a gateway to the RNC. Notice that the Pseudo- Wire gateway aggregates and delivers consolidated ATM flows to the RNC. This functionality, taken with the IMA capability in the Pseudo-Wire access devices, obviates the need to pass the HSDPA traffic through a legacy ATM switch at the RNC location. The AXN gateway furnishes STM-1 interfaces (VC4) to deliver the consolidated ATM flows directly to the RNC. - Page 5 of 8 -

6 Benefits Enables smooth growth of backhaul bandwidth at lower cost than E1 leased lines Overcomes the limitations of symmetric TDM lines for asymmetric data services AXN solution with ATM and IMA available TODAY Fully interoperable with existing equipment at the NodeB and the RNC ATM switch needed only to aggregate leased-line E1s with 3G voice traffic Transparent to NodeB remote monitoring and configuration procedures No risk certified and supported by top-tier mobile equipment vendors Ready for Next-G services and voice+data convergence Beyond ADSL As described in the previous sections, Axerra s Pseudo-Wire solution is ideally suited for HSDPA offload using ADSL2. Perhaps most compelling is that this solution represents a futureproof investment beyond ADSL. It can be deployed today to offload HSDPA traffic using ADSL, but it can also enable backhaul over newer, higher-capacity transports and support true convergence of every generation of voice and data mobile service. The Axerra Pseudo-Wire solution that is deployed for ADSL2 offload is ready today to support the transport technologies and new mobile services described in the following paragraphs. While ADSL is a logical technology for offload of HSDPA traffic, many see it as only a first step. A number of questions remain unanswered regarding the overall capacity of ADSL to handle the expected quantity of HSDPA subscribers, both in the aggregation network and the last-kilometer link to the NodeB site. ADSL2 transport in the last kilometer can typically furnish 8 Mb/s of downstream bandwidth and 2 Mb/s of upstream bandwidth. Given typical oversubscription ratios, these last-kilometer link speeds are expected to support growth of HSDPA services for some time. However, in the aggregation network, existing DSL networks (both the ATM-based and the Ethernet based) have already been architected with significant oversubscription ratios for fixed line ADSL services. These oversubscription ratios are often as high as 50x for residential consumers and 20x for business customers. Overlaying mobile services on top will surely stress the capacity of these DSL networks with yet another layer of oversubscription. In addition, HSDPA is itself only a first step. While HSDPA is well matched to the downstream rates of ADSL2, new generations of services, including HSUPA and beyond, that offer ever greater speeds, especially in the upstream direction, are already on the horizon. A number of operators, including T-Mobile, Telecom Italia, and Cingular, have mapped out near-term plans to test and introduce HSUPA services. However, it appears certain that a new generation of backhaul beyond ADSL is needed to handle these services. New Transport Technologies Several new technologies have emerged that can meet the challenge of next-generation backhaul beyond ADSL, including VDSL, copper bonding using Ethernet in the First Mile (EFM based on IEEE 802.3ah), and Carrier Ethernet over optical fiber. As described in the following section, the Axerra Pseudo-Wire solution is ready today to take advantage of these new transport technologies, while simultaneously converging both voice and data traffic onto a single RAN architecture. - Page 6 of 8 -

7 This figure shows AXN10 Pseudo-Wire Access Devices deployed at cell sites using VDSL, EFM, and optical Ethernet for backhaul transport. The AXN10s use Ethernet to connect to a VDSL modem, an EFM demarcation device, or directly to the optical Ethernet network, respectively. At each cell site, the AXN10s connect to both NodeB and BTS equipment, enabling backhaul of GSM, R99, and HSDPA traffic over any of these transport technologies. Each AXN access device offers not only E1 interfaces for ATM service emulation, but also E1 interfaces that can be configured for circuit emulation service (CES) to support the Abis interface for 2G services. In addition, all AXN access devices provide customer facing Ethernet interfaces for future service needs, such as WiFi or WiMAX hot spots, as well as connectivity needs specified for the R5 NodeB. While VDSL, EFM, and optical Ethernet are all supported for last-kilometer transport to the cell site, typically each of these technologies would funnel into a switched Ethernet or IP/MPLS network. VDSL would use an Ethernet DSLAM, while EFM may use stackable EFM termination nodes, and optical Ethernet may use a carrier-grade Ethernet aggregation multiplexer. Traffic hand-off from the Carrier Ethernet network to the Pseudo-Wire Gateway at the RNC/BSC is typically performed using Gigabit Ethernet. The AXN1600 or AXN800 Pseudo-Wire Gateway offers not only ATM STM-1 connectivity, but also channelized E1 and channelized STM-1 ports for interfacing to legacy BSC equipment. In GSM applications, the CES Pseudo-Wires (that originated as E1s with Abis at the BTS) are transported across the packet network and then consolidated in the AXN gateway into TDM bit streams on STM-1 or E1 interfaces to connect with the BSC. As stated before, this diagram shows multiple generations of mobile services being carried over a single converged RAN. But also notice that both voice and data are carried over this packetbased RAN. In fact, there is no E1 or SDH transport used at any of the cell sites. With no SDH in the backhaul network to furnish synchronization, the Pseudo-Wire solution must supply very accurate and reliable clocking at the BTS and the NodeB. Accurate, jitter-free - Page 7 of 8 -

8 clock sources are critically important for both GSM and UMTS services. Axerra s High Precision Clock Recovery (HPCR ) solution obtains clocking from the BSC or RNC and extends the timing across the Carrier Ethernet packet network. Axerra s HPCR solution is proven to meet the demanding ITU-T G.823, G.824 and G.8261 deployment case 2 synchronization requirements for quality and accuracy (tested and verified to 15 ppb) needed for packet backhaul of mobile services. Pseudo-Wire Solution Ready Today With all of this functionality available today in Axerra s Pseudo-Wire solution, the result is that multiple generations of service can be aggregated onto a single Carrier Ethernet network. Axerra s Pseudo-Wire solution uniquely combines circuit emulation and service emulation (TDM plus HDLC, Frame Relay, and the ATM needed for 3G UMTS and HSDPA) to enable backhaul of any combination of 2G, 2.5G, and 3G voice and data traffic, as well as subscriber Ethernet interfaces for 4G traffic backhauling, all over a single packet RAN. Axerra s Pseudo- Wire solution is ready today to support all of these backhaul options, ready today to backhaul every generation of voice and data mobile services. Axerra Networks full-service Pseudo-Wire solution enables all generations of both voice and data over Carrier Ethernet, enabling mobile wireless providers to realize the true promise of convergence in the RAN and immediately profit from significant OpEx savings. Benefits Supports convergence of all generations of voice and data mobile services on a unified packet network AXN solution with ATM and IMA available TODAY Supports GSM Abis and UMTS Iub interfaces TODAY No ATM switch required at the RNC location Ensures synchronization with the industry s most robust and accurate clock recovery mechanism for packet backhaul No risk certified and supported by top-tier mobile equipment vendors Creates a single optimized RAN for 3G All-IP Axerra Networks furnishes the industry's most complete range of service aggregation and Interworking solutions. Axerra's multiservice over packet (MSoP) technology enables incumbent carriers, mobile/wireless operators, and cable/msos to extend both profitable legacy and emerging services over their Carrier Ethernet networks, such as: IP/MPLS, Ethernet, DOCSIS HFC networks, etc. For more information visit Axerra Networks web site at: Note: This document is provided for informational purposes only and may be subject to change without notice Americas EMEA APAC General Inquiries SalesAmericas@axerra.com EMEA@axerra.com APAC@axerra.com info@axerra.com Addresses, phone numbers and fax numbers are listed on Axerra s website: Axerra Networks, Inc. All rights reserved. Please recycle # Page 8 of 8 -