LTE: An Introduction

Feature Article



WiMAX Concerns

To the service provider, the benefits of WiMAX as clear, assuming subscribers. But, to win subscribers will take some education. After all, most people only have a bare bones understanding of WiFi, if they have broadband at all. So then, being able to address questions and concerns about WiMAX becomes a key to its successful deployment.

Quality of Service

QoS is ultimately the determining factor in a technology’s ability to deliver today’s high-bandwidth services, like VoIP and IP video services, as well as other collaboration-enhancing applications. In order to provide QoS, WiMAX providers must be able to ensure low latency.

The simple fact is that WiMAX service suffers from nearly no latency across its wireless connections — less than 10 milliseconds from tower to receiver. The majority of any latency occurs from the receiver onward, to servers and end users. Thus, as with any broadband service, it is incumbent upon the business to ensure its network equipment is properly set up to handle these services, and upon service providers to provider the appropriate technology to residential subscribers — as they do today.

Security

Considerable attention has been given to network security of late, and WiFi deployments, in particular, have come under heavy scrutiny for their lack of appropriate security. WiMAX, on the other hand, has been designed to provide effective security in order to prevent network intrusion and access violations.

WiMAX security is defined in the Privacy Sub-layer in the MAC Layer, as specified by WiMAX standards. Fixed WiMAX (802.16-2004) typically uses X.509 certificates for authentication and 56-bit Digital Encryption System (DES), while Mobile WiMAX (802.16e-2005) uses EAP for authentication and Advanced Encryption System (AES) for encryption. Both employ Privacy Key Management (PKM) for authentication between base station and subscriber station.

Reliability

The “Five 9s” scenario for network uptime has become the dominant standard for providers when describing their network availability and uptime. However, while landline providers’ networks may, in fact, be capable of such reliability — which equates to something like five minutes of downtime per year — other factors can cause substantial service outages. Specifically, landline service relies on wires running to the home or business, which represent a single point of failure — barring several incoming lines, which is a costly proposition. Because it provides wireless connections to customer premises, WiMAX eliminates the potential for fiber and cable failures, which, technically, are not a result of a provider’s network failure. Instead, by deploying redundant transmitters to cover an area, WiMAX providers can easily provide network redundancy, while, at the same time, expanding their service area with the same equipment.

Also, by using only licensed spectrum, service providers can be assured they are not competing with other carriers for network resources. And, since WiMAX radios a predicted to have a lifespan of more than four decades, WiMAX can also be sold as an effective disaster recovery solution.

Interference

It’s no secret that wireless signals are susceptible to interference — it’s the nature of the beast, and it’s a factor that has required attention from providers since the first wireless devices. Even now, older, 2.4GHz cordless phones and other home appliances have the potential to disrupt WiFi signals.

Employing counter-interference measures is something providers need to manage, and it really means nothing more than understanding the potential sources of interference within the electromagnetic spectrum, and engineering solutions to work around those obstacles.

There are two general types of interference: Out-of-channel interference is a result of other transmitters that are not on the same frequency as the primary radio; and co-channel interference results on the same frequency as the original signal.

To eliminate co-channel interference, precautions must me taken to plan frequency use appropriately, use only licensed spectrum, and provide dynamic frequency selection. Out-of-channel interference can largely be avoided through the use of OFDM and OFDMA technologies, as well as any of a variety of antenna designs specifically developed to avoid interference from other devices.

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