Ruckus Wireless recently talked to us about how 802.11 wireless local area network technologies can be improved to reliably distribute IPTV - even in the areas where many Wi-Fi networks are present. New technology now exists that makes it possible to enhance the 802.11 system to deliver a predictable Wi-Fi signal, focusing signals over the best quality path through the air to specific receiving devices, avoiding interference and increasing range, performance and reliability.

What is Wireless Distribution of IPTV Signals?

With all the new digital information, wrapping in the Internet Protocol, in-home distribution has become a major issue for both consumers and providers. Wi-Fi is clearly the desired mode of transport but hasn't  lived up to expectations relative to real-time video distribution. Wi-Fi distribution of IPTV streams from broadband providers is the use of unlicensed radio frequencies to distribute multimedia signals to IP-enabled receiving devices in a home or nearby location.

Moving IPTV streams around the home using new "smart Wi-Fi" typically involves combining smart antenna technology that determines the best path through the air for any given traffic type with the prioritization and management of multimedia signals. This ensures that, even in an ever-changing environment, that IPTV streams can predictably be received and viewed at the highest possible quality.

Figure 1 shows how an in-home Wi-Fi system can be used for IP Television (IPTV) premises (home) distribution. This diagram shows that a broadband modem is installed in the home that has WLAN with premises distribution capability. This example shows that the broadband modem is located at a point that is relatively far from other devices in the home. The broadband modem is connected to a wireless access point (AP) that retransmits the broadband data to different devices through the home including a laptop computer, Wi-Fi television and an IP set top box (IP STB) that has a built-in Wi-Fi receiver. 

Figure 1

Why is Wireless IPTV Distribution So Important?

Wi-Fi distribution is important because no that voice, data and IPTV is coming into homes over the broadband connection, there's no easy and efficient way to get this digital multimedia information where you need it. For example, many consumers in Hong Kong and Italy have already refused new IPTV services due to rewiring or having to retrofit their homes to support it. Even viable wired solutions such as IP over power lines and coaxial cables are costly, disruptive and often suffer from interference and reliability issues. Smart Wi-Fi was developed to solve these problems.

IPTV over Wi-Fi is a preferred method of IPTV distribution in the home because it allows the most freedom and flexibility for both the subscriber and the provider. It also effectively eliminates the cost and hassle of wiring and/or re-wiring the home. Consumers are enamored with Wi-Fi and would prefer a single infrastructure in their homes for all their multimedia - if they could get it.

What Kind of Challenges Exist for IPTV Distribution over Traditional Wi-Fi?

Until recently, reliable distribution of IPTV signals over consumer-grade Wi-Fi systems have not been possible. Wi-Fi is fundamentally an unreliable medium due to that fact that it is shared among multiple users over the unlicensed RF spectrum. The key challenges that face providers and subscribers running IPTV over Wi-Fi is radio signal interference from other sources, signal quality levels, range and data transmission rates.

Radio interference can cause lost packets. This results in sub-standard video that freezes or has an unacceptable amount of artifacts.

Sources of WLAN interference are varied and many including microwave ovens, baby monitors, cordless telephones, neighboring Wi-Fi networks and even people.

Signal quality is determined by a variety of metrics such as signal strength, packet error rates and distortion that occurs between wireless communication devices. Lost packets cause artifacts or frozen video.

The Ruckus system increases the data transmission rates and range in a physical area using directional beam-forming smart antenna technology that focuses Wi-Fi signals toward the receiver over the best possible signal path at any given time. If the signal path is disturbed, Ruckus claims its system will automatically steer Wi-Fi beams in a different direction to ensure consistent video transmission quality.

Figure 2 shows typical types of unlicensed radio transmission systems that can cause interference with WLAN systems. This example shows that there are several different communication sessions that are simultaneously operating in the same frequency band and that the transmission of these devices are not controlled by any single operator. These devices do cause some interference with each other and the types of interference can be continuous, short-term intermittent or even short bursts. For the video camera (such as a wireless video baby monitor), the transmission is continuous. For the cordless telephone, the transmission occurs over several minutes at a time. For the microwave oven, the radio signals (undesired) occur for very short bursts only when the microwave is operating. For the wireless headset, the transmission occurs for relatively long periods of time but the power is very low so interference only occurs when the wireless headset gets close to WLAN devices.

Figure 2

Important Features for Wireless PDN

The features of most importance to the user are those that are masked by the underlying technology. That is to say they are not features the user would tune or touch but rather features of critical important to enabling IPTV within the home. These include the ability for the system to automatically avoid other Wi-Fi interference from neighboring networks, or microwave ovens or other obstructions that may dynamically appear and cause problem in the transmission of video over Wi-Fi. Another critical user features is the ability to support quality of service for special video traffic such as multicast. Multicast is typically handled by the 802.11 protocol as best effort traffic. This means that the receiver sends no acknowledgement and only the bandwidth available at any given time is used. This is simple unacceptable for streaming video or IPTV.

Smart Wi-Fi systems alter multicast traffic by directing the traffic to a specific receiver, forcing that receiver to provide an acknowledgement. This way the system knows if the video transmission was received and the quality of the link. Without a smart Wi-Fi system to support multicast IPTV streams, subscribers will not be able to use IPTV in the home over Wi-Fi. 

Finally, a Wi-Fi PDN must be able to intelligently distinguish between and prioritize different types of incoming traffic. If it cannot, a user watching an IPTV stream, for instance, would have their viewing interrupted when another user is downloading a file over the same Wi-Fi network.

What is the Basic Operation of the Smart Wi-Fi System Developed by Ruckus Wireless?

The Ruckus wireless system combines a smart antenna array and advanced algorithms that control the selection of the antenna with advanced traffic engineering and quality of service software to achieve high-performance and system reliability

The Ruckus system leverages MIMO antenna diversity techniques to provide up to 63 different antenna combinations between any access point and adapter at any given time. Ruckus BeamFlex technology manages how and when the antennas are selected and constantly ranks the quality of each link on a per station basis. In effect, dozens of receiving devices, each with dozens of potential signal paths are monitored and managed.

In turn, the Ruckus system is able to provide interference mitigation or avoidance. If a neighboring network on the same channel causes problems with a particular signal path, the Ruckus system can select a different antenna combination the performs at a higher rate. 

Ruckus Wireless has also developed a traffic engineering engine it call SmartCast. The company claims its software is a superset of 802.11e used to identify, classify, schedule and queue different types of multimedia traffic. SmartCast is used to ensure that different traffic is handled appropriate so, for instance, a large file download doesn't interfere with an IPTV channel being viewed at the same time. SmartCast is also responsible for multicast optimization.

Figure 3 shows how WLAN systems can be improved through the use of directional transmission and media prioritization to provide improved performance. This example shows that a wireless access point has been enhanced to allow the transmission of signals using directional antennas so that signals can be sent to specific devices. In this diagram, one of the best paths between the access point (AP) and Wi-Fi device (e.g. Wi-Fi Television) is not direct as a metal art object that is located between the AP and the Wi-Fi device reflects the radio signal. This example also shows that this WLAN system has the capability to prioritize transmission based on the type of media (such as real time video over web browsing data).

Who Sets Up IPTV Distribution Systems

While home IPTV distribution networks can be set-up by the consumer, just like a conventional Wi-Fi network is setup today. Most consumers will rely upon and prefer to have the broadband provider setup the system to ensure the best possible performance and reliability. For example, PCCW in Hong Kong, the worlds leading IPTV provider with some 500,000 subscribers, provides in-home installation of both smart Wi-Fi as well as wired alternatives.

What type of Equipment is needed for a Ruckus Wireless PDN?

To build a reliable wireless PDN, the only equipment needed is a wireless multimedia router (or access point) and (optionally) a Wi-Fi enabled receiver of some sort. That receiver could be a laptop, set top

Figure 3

box equipped with Wi-Fi capabilities or an IP-enabled PVR. Obviously, for IPTV to be supported, a broadband IP connection from the service provider and a broadband gateway terminating that connection is required. Typically the Wi-Fi multimedia system is attached to the broadband gateway in the office or den. A smart-Wi-Fi receiver is attached to devices (such as a set top box) to ensure predictable connectivity.

Are There any Compatibility Issues?

Ruckus systems can co-exist with traditional LANs or even replace them.

Some of the compatibility issues include how wireless access points support multicast traffic and the ability for set top boxes and other IP-enabled multimedia devices can actually support the Wi-Fi standard. To ensure interoperability, Ruckus Wireless has developed a free interoperability program it calls Ruckus Interoperability and Open Testing (RIOT). This program was developed for third-party manufacturers of IP-enabled multimedia devices such as set top box, game consoles and PVR. All testing is performed by the Ruckus in an in-home test laboratory created for the program.