Mobile Digital TV Antenna Diversity for Indoor and In-Vehicle Reception

Understanding how diversity antenna systems work, and how Mobile Digital TV viewing can be improved through the use of multiple antennae — even for space-constrained portable devices, and for in-vehicle and deep-indoor reception.

By Roy Oren, CTO, Siano Mobile Silicon

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Video/Imaging DesignWire
(10/5/2009 4:00:47 AM)

Digital TV is expanding from home to everywhere – streets, cars, buses, trains, restaurants, the beach – as TV content consumption is changing from a stationary, satellite or tethered paradigm and a group viewing experience towards a more personal viewing experience on portable wireless devices.

The emerging world of mobile entertainment is currently fueled by the consumer demand for anywhere, anytime television viewing, along with growing consumer demand for converged multi-media devices. Offering GPS services bundled with mobile digital TV capability is a primary example of this new trend.

The rise in popularity of in-vehicle mobile TV is not mutually exclusive to the rise in demand for unlimited stationary TV viewing.  The mobile TV revolution born in Japan and Korea has seen huge consumer demand for blanket reception – a trend already evident in China and expected to emerge soon in Europe and beyond.  Antenna diversity can not only solve the technology challenges faced by broadcasting MDTV to vehicles traveling at fast speeds, but also overcome reception difficulties of MDTV in deep in-door locations – another technology challenge for successful mobile TV roll-out. This article explains how antenna diversity can overcome what are arguably the two most problematic MDTV scenarios, deep-indoor and in-vehicle viewing.

The DVB-T challenge
Some of the currently available digital TV infrastructures, especially DVB-T (Terrestrial Digital Video Broadcast) in some countries in Europe, do not enable TV everywhere. Existing DVB-T deployments in Europe were intended for stationary reception using roof-top antennae and as such face issues due to impulse noises, below-roof antenna position environmental disturbances, in-door coverage and of course, mobility. In addition, as long as analog TV (PAL) is still in service, the transmission power of DVB-T towers is limited, in order not to interfere with the analog broadcast.

Recent DVB-T receiver chips introduced to the market partially overcome these problems by introducing very high sensitivity and sophisticated mobility algorithms. Hence, outdoor reception of DVB-T over a mobile device is possible in almost every “covered” location in Europe.

Nevertheless, indoor reception – and especially “deep-indoor” (far away from any window) is more challenging, as the indoor signal strength is weaker, and there is no line-of-sight between the transmitter and the receiver, so the radio signal bounces off various objects to get to the receiver (a phenomenon which is often referred as multi-path propagation).

How can indoor DVB-T reception be made part of the user experience in Europe?
Antenna diversity is a scheme that uses two or more antennas to improve the quality and reliability of a wireless link. The concept is already in use for technologies such as WiFi, wireless microphones, and others. For the DTV application the idea is to use the existing infrastructure and have several antennas inbuilt within the receiver that receive the transmission signal through different propagation paths. Thus, it becomes feasible to receive the DTV signal in spots where single antenna receivers fail to produce a good user experience.

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