Updated: March 15, 2013

Wireless Network Basics
802.11 Variants, Data Throughput and Bandwidth Management

Streaming of Multimedia Content over your Wireless Network


Integrating your PC and broadband Internet connection with your home entertainment system has become easier than ever thanks to Internet-connected and DLNA-enabled HDTVs, Blu-ray players, and media players. Yet, streaming of HD media content is a bandwidth-demanding activity which you need to plan for when designing your network to avoid choppy playback.

This guide to wireless basics explains the different 802.11 variants and their implications in terms of data throughput, handling of multi-media content streaming, 2.4GHz and 5.8GHz dual-band and dual-radio operation, and bandwidth management in wireless networks. In the second part of this article, we discuss wireless security in home entertainment.


 

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Streaming of Multimedia Content

Bluetooth and Wi-Fi Wireless Networking Technology Basics

Wireless connected network devices use either Bluetooth or Wi-Fi wireless technology to access digital content. Both technologies operate mostly in the 2.4GHz band though some Wi-Fi devices operate in the 5.8GHz band. We are also starting to see an increase in Wi-Fi 802.11n devices that support dual-band wireless operation.

Yet there are major differences between Bluetooth and Wi-Fi wireless network technologies both in terms of data throughput, and in the way they handle transmission and security issues.

Bluetooth: Bluetooth primary use is to replace cables between networked devices requiring a low to medium speed access connection over short range. Generally, this is 10m or less though it is possible to extend this range considerably.  Maximum supported download speed when used in half-duplex mode is 732Kbps. Due to this limited data throughput supported by Bluetooth technology, you would not find this type of wireless interface on a wireless media player intended for streaming of real-time HD audio and video content.

Wi-Fi Certified Logo

Local Area Wireless Networks (LAN): Wi-Fi uses the IEEE 802.11 standard with its 'a', 'b', 'g' and 'n' variants to provide wireless high speed access to the internet and other digital content over networked devices in a local area network.

The 802.11b has a maximum data transfer rate of 11Mbps; the 802.11a and 802.11g standards both support a maximum of 54Mbps transfer rate, while the latest emerging 802.11n standard (finally approved in Sept. 2009) supports a maximum raw data throughput of up to 600Mbps.

The data transfer rates referred to above represent the maximum speed at the physical layer. The maximum effective data throughput supported by a wireless network available for the end user at the application level is substantially less.

The higher data rates supported by the 'a', 'g', and 'n' variants explain why wireless home entertainment systems and wireless media players designed for video streaming utilize the faster 802.11a, 802.11g, or 802.11n standards instead of the slower 802.11b wireless networking technology. In addition, when it comes to streaming of HDTV content, the only recommended Wi-Fi standard is the 802.11n since HDTV requires anything between 8 and 19Mbit/s of bandwidth over the wireless network for the HDTV link alone.

Apart from the difference in data throughput between the different 802.11 variants, there is also a significant difference between these standards in the supported wireless range, with the shortest range being that supported by devices in the 5.8GHz band.

The table below summarizes the main differences with respect to operating frequencies, data rates, and range, as applicable to these IEEE 802.11 variants:

802.11 Variant Operating Frequency Data Rate Range (typical)
Max. Typical Throughput Indoor Outdoor
'a' 5 GHz Band 54 Mbit/s 22 Mbit/s 30m / 98ft 100m / 330ft
'b' 2.4 - 2.5 GHz 11 Mbit/s 4 Mbit/s 36m / 118ft 125m / 410ft
'g' 2.4 - 2.5 GHz 54 Mbit/s 20 Mbit/s 36m / 118ft 125m / 410ft
'n' 2.4GHz and/or
5.8GHz
600 Mbit/s

(see note below)

50 - 150 Mbit/s 70m / 230ft 200m / 660ft

Note:

Reaching 600 Mbps with the 802.11n standard requires 4x4 MIMO (multiple-input multiple-output) operation, a double-wide 40 MHz channel, and using the new Short Guard Interval (SGI) to reduce time between transmissions. In reality, most of today's 802.11n APs have a top raw data rate of 300-450 Mbps.

Directly related to the raw data throughput with 802.11n gear is the typical data throughput referred to in the above table. Reaching the 150Mbits/s typical data throughput is possible with dual-band devices operating either in the less congested 5.8GHz band, or with simultaneous dual-band operation.

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802.11n is the fastest in the range of Wi-Fi standards; it is being extensively used on the latest wireless media players as it has enough bandwidth to stream HDTV content without choppy playback even in high traffic Wi-Fi spaces.

The high throughput of the 802.11n wireless network technology is possible thanks to the use of Multiple-In-Multiple-Out (MIMO) wireless transmission technology, a 40MHz bandwidth instead of the 20MHz used by the other standards, and a reduced time interval between transmissions.

Dual-band and Simultaneous Dual-band (or dual radio)

802.11n gear may operate in either 2.4GHz or 5.8GHz bands. Some gear comes as dual-band; a typical case is that of the new Apple TV wireless media player; the 2010 version of the Roku media player, the Roku XD|S also support 802.11n dual-band operation. (For more information on the new Apple TV and the Roku XDS, please refer to our review here.)

Obviously, to use these wireless media players in the less congested 5.8GHz band, you need a wireless access point, or AP (typically this takes the form of a wireless router with integrated AP and Ethernet switch) that supports either dual-band operation, or better still, use one that comes with dual radio.

Dual-band operation means that the wireless AP should be able to support operation in both the 2.4GHz and 5.8GHz bands; but once set, you will only be using either one band or the other. In other words, if you choose the 5.8GHz band to communicate with your dual-band wireless media player, you will not be able to support any 2.4GHZ wireless networking devices.

To support both, you need a wireless access point with dual-radio support, i.e. one that is capable of simultaneously operating in the 5.8GHz and 2.4GHz bands.

5GHz Frontier ...what are the pros & cons of 2.4GHz vs. 5.8GHz Wireless Network operation?

The 2.4GHz band is more congested - not just because of other Wi-Fi equipment in the home and neighboring wireless networks, but also because of the many devices like cordless phones and microwave ovens. This renders the 2.4GHz band more prone to interference.

On the contrary, the 5.8GHz band is relatively under-utilized, meaning that the latest wireless standard could have very well avoided all the congestion in the 2.4GHz band should it have mandated 5.8GHz operation; yet the standard leaves this open to manufacturers' choice. The issue is not just congestion but even more so - reduced effective data throughput since a congested wireless environment would not enable these high speed devices to operate full-time at their maximum sustained higher data rates.

The result... consumers buying expensive 802.11n gear operating in the 2.4GHz band would not attain the higher speeds they were hoping for in real-life application.

Thankfully, manufacturers are starting to realize the benefits associated with 5.8GHz operation and are coming up with dual-band wireless equipment to enable users enjoy the maximum benefits of the new 802.11n standard.

There is only one drawback: 5.8GHz devices support a slightly shorter range as transmission at these higher frequencies is more prone to signal attenuation due to walls, ceiling, furniture, etc. This may lead to a drop in the effective data rate over the wireless link at the extreme ranges.

Wireless Network Bandwidth Management

Another issue worth planning for when investing in a wireless media player is that of bandwidth management of your wireless network. Actually, this is something you have to plan for when designing your network.

There is a limit to how much data you can move across a network; this is independent of the wireless media player or any other wireless device you are using.

Bandwidth requirements by the different applications running over a network have to share from the same overall bandwidth available for use by the different applications at any one particular time.

Furthermore, if your data needs to make a double hop because both your source (e.g. PC) and receiver (e.g. wireless media player) are connected to your network via a wireless setup, then this will double your bandwidth requirements.

Thus, when streaming bandwidth-demanding content, such as high definition video and audio, there is a higher risk of suffering from choppy playback when streaming over a crowded wireless environment.

To help in these circumstances, some wireless APs (routers/switches) include quality of service (QoS) support. This feature allows you to prioritize certain traffic to minimize contention related problems in a crowded air-space when handling real-time applications such as VOIP and multi-media content.

In the second part of this article, we discuss security issues in wireless home networking as well as steps you should take to improve the security of your wireless networking activity. Security in wireless networking is becoming more critical as the use of wireless technology is increasing in popularity. This security issue applies irrespective of whether it is a laptop connecting to a wireless network in the home, or setting up a wireless digital media player as part of a complete home entertainment solution.



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