laying the groundwork for wimax

Thinking About Laying the Groundwork for WiMAX Early trial results show wireless performance on par with T1 technology and expose early network integration considerations. subscriber antenna and the carrier’s base station, quality of service (QoS) and a number of other advantages. 802.16-2004-certified is currently transitioning from a technical trial of early WiMAX access technology that involved a handful of customers and pre-standard systems are expected to deliver 75 Mbps per channel (shared) across a 3-to-10-kilometer coverage range in a 20MHz channel. equipment to one involving more than a dozen customers and standards-compliant equipment. The early trial that is currently concluding centered around basestation equipment, operated by in Middletown, N.J., which was The primary goal of the first technical trial was to test the viability of the emerging wireless network as a potential access service by built before ratification of the 802.16-2004 standard, however. As such, the trial was for proof-of-concept purposes and was considered comparing it with T1 technology in terms of reliability and performance. The early trial indicated that WiMAX is on par with T1 technology in a “pre-WiMAX” test of network availability and performance metrics, as well as a check for integration issues with existing enterprise terms of the key network performance metrics: latency, jitter, throughput and packet loss (see Table on page 2). networking equipment. It involved three customers. The next trial, beginning in December 2005 in Atlanta with about 15 customers, will use equipment that has been built to the 802.16-2004 specifications. Also, getting both carriers’ and customers’ feet wet with WiMAX has helped expose some integration issues with existing routing systems, Another version of 802.16, 802.16e, is a mobile version of WiMAX and is considered an extension of 802.16-2004. If and when deployed by primarily in the proper configuration for active/standby connection failover. Learning about these in a test scenario has educated carriers, 802.16e-based services will compete with 3G and other mobile data services. 802.16e is not part of the current WiMAX trials. participants so that they can be aware of how to best integrate WiMAX into their existing networks, should they decide eventually to go live with a commercial service. Standards and Equipment Update Many of the Middletown test variables, such as the CPE and, in some cases, the transmission frequency used, would change in a What Is WiMAX? The term “WiMAX” is short for Worldwide Interoperability for Microwave Access. It refers to Institute for Electrical and Electronics Engineers (IEEE) commercially deployed service. The reason is that standards-compliant 802.16-2004 WiMAX products have only recently begun shipping and 802.16 standards for broadband wireless last-mile technology. The trials involve one of two versions of 802.16, called 802.16-2004. were not yet available at the time that the Middletown trial began in the spring of 2005. 802.16-2004 standards specify a form of “fixed” wireless broadband communication from a stationary subscriber location to a carrier’s The first product certifications for 802.16-2004 standards compliance and product interoperability are expected in late 2005 under the auspices base station on a cell tower. Services based on this last-mile technology can be thought of as a wireless broadband alternative to wired broadband DSL and cable modem services. of an oversight organization called the WiMAX Forum. The Forum, an industry consortium of about 220 companies in WiMAX-related businesses, has engaged a lab called Cetecom headquartered in Malaga, Spain, to conduct testing for interoperability among 802.16- The 802.16-2004 standard was ratified in June 2004. It incorporates a specification for indoor customer premises equipment (CPE), 2004-compliant products. encryption, non-line of sight (NLOS) communications between the WiMAX-compliant equipment is being built for both licensed and unlicensed frequencies, though and its pre-trial customers agree Comparative Pre-WiMAX Performance Measurements that using licensed spectrum will be necessary for delivering carrier- class services with accompanying Service Level Agreements (SLAs). The first products are being WiMAX Forum-certified in the 2.5GHz and 3.5GHz licensed bands and in the 5.8GHz license-exempt band. The Metric T1 Benchmark WiMAX Performance trial took advantage of spectrum it could borrow for its early trials, including the 700MHz band, licensed to broadcast TV operators, Availability 99.99% 99.97% Packet Loss <.1% <.1% and the 2.5GHz band. Throughput 1.5 Mbps 1.3 Mbps Technology Trial Architecture Pre-standard WiMAX base station equipment was installed in two Middletown, N.J., cell towers. The base stations communicated by Jitter Latency No benchmark 17 milliseconds <10 milliseconds 14 milliseconds airlink over approximately 2 miles to customer sites and via a 38GHz encrypted microwave link to an network operations center (NOC). From the NOC, traffic was routed to and from trial customers’ other enterprise sites across the production The lead network architect at one trial customer commented that this could be a valuable attribute if his company, a retailer, were to acquire IP-Enabled Frame Relay network, as all trial customers were users of the IP-Enabled Frame Relay service. a chain of stores using a different network service provider. Using WiMAX, he said, the company would likely be able to convert the newly acquired sites much more quickly to its own network service. At the customers’ locations, a rooftop-mounted transceiver was cabled to an indoor, modem-like subscriber data adapter. The adapter WiMAX also can be jacked up to higher speeds than cabled T1 services for easy scaling to multiple megabits per second. And the early tests plugged into an Ethernet switch, which connected to an VPN appliance for IP Security (IPsec) encryption using the Advanced showed performance metrics for network availability, packet loss, throughput and latency on par with benchmarks for T1 technology Encryption Standard (AES) algorithm. The encryption appliance was part of the configuration because the pre-standard WiMAX CPE had (see Table above). not yet been built to perform encryption. The NetGate appliance connected to the customer’s router, which connected to the T1/frame relay service (see Figure on below). Integration Issues Two of the trial customers had issues with their routers failing over between their test WiMAX connection and their production frame relay Provisioning and Performance Despite the early, pre-standard WiMAX conditions, customers learned that as a technology, WiMAX holds promise for faster provisioning than connection. In one case, the company learned that its current router operating system supports dial backup only. This meant that the company would have to upgrade its routers to the next higher version of OS if it were to deploy any kind of diverse WAN support, including cabled T1 connections. They experienced half-day to one-day installation times, compared with 30- to 45-day provisioning times for cabled circuits. WiMAX, T1, DSL or anything else other than dial. Prototypical Technology Architecture Typical Pre-WiMAX Customer Trial Site Pre-WiMAX Trial Service Area 2.5GHz (Middletown, N.J.) WiMAX Radio and Antenna 700MHz Subscriber Data Adapter (WiMAX Modem) Base Station Ethernet Switch Base Station 7100 (Encryption) NOC Frame Relay DS1 Customer Router The Promise of WiMAX Interference Experiences How does a wireless link compare, performance-wise, to a wired link simply because of its exposure to atmospheric conditions and •Performace equivalent to T1 as far as availability, packet loss, latency and throughput interference? •Can achieve speeds higher than cabled T1 As noted, the pre-WiMAX trial was conducted in some locations in the licensed 700MHz band, which the Federal Communications •Dramatic reduction in provisioning times Commission (FCC) has set aside for broadcast TV channels. pinpointed interference coming from a TV station in Riverhead, N.Y., as •Potential for broad and growing footprint causing bit-error rates that resulted in sporadic link losses for 2 to 5 seconds at a time. That enterprise currently runs a 128-Kbps IP-enabled frame relay connection from its trial site, and its IT staff says the company would removed the 90-degree antenna it was operating on its base station and installed a Yagi antenna – a focused, unidirectional consider WiMAX as either a primary or backup link, depending on the needs of each of its locations. Alternatively, WiMAX could serve as a antenna commonly used in communications when a frequency is above 10 MHz – and directed it straight at the trial site experiencing the interference, which alleviated the problem. second active link, depending on commercial pricing models. In such a case, one connection could potentially support a particular type of traffic, such as FTP, to prevent congestion on the other connection. The Yagi antenna solution in a commercial deployment, however, wouldn’t be ideal, because it would limit coverage to other customers. The lead architect at this trial customer, the retailer, notes that it is difficult to find a consistent broadband access option, such as DSL or In a real-world scenario, would obtain fully licensed coverage for delivering services and work out with the interferer whatever was cable modem, across all geographies needed to serve his stores. He hopes that the WiMAX service footprint will be more widespread, given needed to clear up the interference, according to Labs engineers involved in the trial. that it is easier to provision than cabled options, which require digging trenches and obtaining rights of way. If he can get an SLA with Conclusions and Next Steps The primary conclusion of the pre-WiMAX trial based in Middletown was that WiMAX technology performs as reliably as T1 technology in WiMAX, “so much the better,” he says. At another trial customer’s site, the customer experienced an outage with the NetGate 7100 VPN appliance, used for encryption. Pre- terms of availability, latency, jitter, packet loss and throughput. The Atlanta trials will test equipment that has been designed in WiMAX equipment does not support encryption, and data in the early trials would have been transmitted in the clear across the compliance with the ratified 802.16-2004 standards. wireless access link if special steps were not taken to protect it. So set up its trial customers with its Network-based IP-VPN Though 802.16-2004 specifies support for data encryption within the WiMAX CPE, the ANIRA service will still be in place for many customers, Remote Access (ANIRA) service. because the available WiMAX-compliant CPE supports Data Encryption Standard (DES) or Triple DES algorithms, which many upcoming trial ANIRA is a network-based managed security service that encrypts customer data from the back end of the customer router and across companies do not consider strong enough to meet their needs. The U.S. National Institute of Standards and Technology (NIST) selected AES the access link (in this case, the WiMAX air link) to’s IP-Enabled Frame Relay backbone network using an IPsec tunnel. as the U.S. government’s official encryption standard in November 2000, and it is considered the strongest algorithm available. In the In the case of the second customer, the connection didn’t fail over from the WiMAX link to its frame relay link automatically for security network in the Atlanta trial, wireless backhaul between WiMAX base stations will be used in some places, and AES encryption will run over those links. purposes when the NetGate 7100 failed due to a software bug that has since been fixed. The customer’s router, using Border Gateway One pre-WiMAX trial participant has expressed the need for quality of service (QoS) capabilities long-term to support latency-sensitive Protocol (BGP) and CiscoEnhanced Interior Gateway Routing Protocol (EIGRP) routing algorithms, still saw the WiMAX link as the best path applications such as voice over IP (VoIP) and, eventually, video and multicast applications. QoS is not addressed in pre-standard WiMAX and continued to forward traffic over it. So the company had to manually shut down the WiMAX interface. equipment. However, the 802.16-2004-compliant equipment to be used in Atlanta supports QoS-standard capabilities called Scheduling Access. This trial participant rated the WiMAX bandwidth as “better than frame.” As specified in standards-compliant equipment, the base station in the carrier network controls access priority from the subscriber equipment. equipment has been a major goal with next-generation broadband wireless access equipment in general to ease and accelerate The Scheduling Access capabilities are intended to prioritize traffic into four queues, with maximum latency and tolerated jitter specified first, deployment and to lower service provisioning costs. such as VoIP without silence suppression. From there, the priority queues range down to best-effort traffic. Transitioning to standards-based equipment that eases deployment and begins to build economies of scale for WiMAX technology – both in’s Atlanta trial and elsewhere throughout the industry – will no doubt prove to be a pivotal next step in evaluating the merits of The Atlanta trial will also shift from using mostly line-of-sight equipment and outdoor transceivers, whereby antennas must be able WiMAX as a last-mile contender. to“see”’s base station to send and receive signals, to some non- line-of-sight and indoor equipment. Non-line-of-sight, indoor
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