How will Mobile TV work when we hide out indoors or in the subway? Dr Peter Raabe, Radio Frequency Systems Global Product Manager – Wireless Indoor Solutions, explores the options
Just as consumers expect mobile phone and wireless data coverage everywhere indoors and underground, they will have the same expectation of broadcast mobile TV and WiMAX services–particularly since these will be received on the same multi-functional handsets. In fact, it is expected that the vast majority of mobile TV and wireless data interaction will take place ‘indoors', in venues such as homes and office buildings, plus busy public metros, shopping centres and airport terminals. Consequently, carriers are already exploring the level of coverage that will be required in these so-called confined spaces, and how to achieve it.
The practical approach will be to obtain as much coverage as possible from the outdoor network, which will be the starting point for deployment. But, although people's homes and some office buildings may be serviced in this way, a great many other key venues cannot be adequately penetrated by the outdoor network signal. This calls for the deployment of dedicated RF infrastructure to distribute the signal indoors.
Fundamentally, the principle of achieving wireless indoor solutions for broadcast mobile TV and WiMAX is no different from 2G, 3G and WiFi networks. Indeed, many key buildings around the region already have confined coverage infrastructure in place to support mobile phone, wireless data, and various radio services. These generally take the form of passive or active broadband distributed antenna systems (DAS) that support multiple services and carriers, and which now can be leveraged to provide coverage for broadcast mobile TV and WiMAX as well.
Adapt and adopt
One of the challenges will be adapting the existing systems to provide optimum coverage for these next-generation services. Take broadcast mobile TV in the first instance. Digital video broadcast to handhelds (DVB-H) mobile TV services are likely to be deployed in either the UHF or S-Bands. The UHF band (~470-720MHz) is close to the 800 and 900MHz cellular bands, so similar RF signal propagation and cable loss characteristics can be assumed. The S-Band (~2200MHz) is more likely to exhibit behaviour similar to the UMTS 2100MHz band.
WiMAX, on the other hand, operates at frequencies up to 6GHz–including the licensed and unlicensed 2.3-2.7GHz, 3.3-3.7GHz and 5.1-5.8GHz bands. At these higher frequencies, both signal propagation and cable loss characteristics are likely to be quite different, providing new challenges for coverage planners.
The other coverage planning issue that must be taken into account is that of how strong the signal needs to be for handset reception. This will vary significantly depending on whether the subscriber is stationary (such as sitting in an airport terminal), or moving (such as sitting on a subway train). In addition to signal level, both mobile TV and WiMAX reception at high speeds are highly dependent on the number of signal carriers and the type of signal modulation used.
The interaction of the indoor ‘microcell' with the outdoor network must also be considered in order to minimise interference. It is likely that mobile TV services in a given region will be allocated a single RF channel operating in single-frequency network (SFN) mode. Owing to licensing restrictions, this is anticipated to incorporate any indoor microcells as well as the outdoor network.
Conventional outdoor SFNs operate using complex signal timing and strict power levels to avoid co-channel interference. Although network planning is a challenge, the finely tuned network is essentially static once on-air. The introduction of indoor SFN microcells creates a dynamic environment that must therefore be carefully controlled, lest the balance of the total SFN is disrupted. Conventional indoor planning targets the indoor signal being stronger than what penetrates from outdoors, but when operating in SFN mode it is also important to exert strict control over the signal timing and power levels to ensure optimal coverage is achieved without interference.
Infrastructure evolution
Despite the broadband nature of much of the existing RF infrastructure, there is still much development work being done to allow systems to be upgraded in support of the new services. The heart of an indoor network is typically a broadband passive DAS, comprising broadband radiating cable or a distributed antenna network, which provides contoured RF coverage of a given confined area. These have evolved to be ideally ultra-broadband, allowing all services from 30MHz to 6GHz to share the same passive distribution system.
Wireless indoor solutions also incorporate many different active components that need to be fully functional in the new frequencies and bandwidths specified. These include repeaters and amplifiers to support RF-over-fibre systems, which are utilised in larger buildings and complexes where purely passive infrastructure is insufficient. In addition, methods of collecting the mobile TV or WiMAX signal for distribution indoors need to be considered. These typically include, besides BTS/transmitter combining systems in multi-band multi-service applications, either an off-air repeater and donor antenna assembly, or else a dedicated ‘customer premises equipment' (CPE) installation in the case of WiMAX.
As both WiMAX and mobile TV technologies gather momentum, the fact that consumer interaction will take place to a large extent indoors cannot be overlooked from both a network revenue and customer satisfaction point-of-view. This means the need for wireless indoor coverage has emerged as an essential factor to be considered in the overall business case. The successful realisation of such wireless indoor solutions will demand careful network planning and optimisation of both indoor and outdoor networks, supported by state-of-the-art wireless infrastructure.
Never mind TV – get into video
vTap from Veveo is a service that searches and indexes 115,000 web sites that carry large amounts of mobile video – totalling about 150 million video clips. It then encodes those videos on the fly to users who request them from their mobile device, using their vTap application. Its deployment could help operators unlock latent demand for access to user generated videos on the web, according to Guru Pai, VP of Marketing and Business Development, Veveo??"The free web video segment is a domain that's exploding," said Pai, "but it is disorganised and fragmented. We organize and find content, so we can deliver relevant video to our users regardless of whether they have carried out a specific vide search or are just browsing for content."??"Veveo has been active for a while in the internet but we now plan to do this in the mobile domain," Pai said. "There is increased complexity in terms of user input and display, but a user can find and view any content on the web in our index and then play it on their phone."??Users can either set up a profile on vTap, allowing the service to build up a list of recommendations and so on, or they can browse the index which is organized into about three million or so topics. All the main free internet sites plus news providers and TV sites are included in the index, Pai said.. The service carries out the on the fly transcoding and matching to which player the device has. ??Users can either take the service as a client on their phone, or as an xhtml solution. Pai said Veveo has an announced agreement with Motorola to include to client in its handsets, and has others agreed with other manufacturers that he can't reveal. The application would be somewhere inside a handset Video menu structure, he reckoned, or even on the browser page itself. ??Veveo's business case is to make money through advertising, with Pai currently saying it is in "audience building" mode. ?"Several ad networks think we've got something different," he said, "because either we have user profiles or targeted user queries. We can interleave ads with search requests or have ads on each xhtml page to interface with the rest of the mobile advertising industry."??As for the operators – they may need to change their business approach to video, Pai admitted, to benefit from such an app. If you look at operators like Verizon, it has about a thousand videos in a walled garden at any time, we have 150 million in our index" he said.?"I think operators are trying to figure out the video market. For linear TV they can address that through broadcast mobile TV, which has its place. But the non-linear user generated content world has hundred of millions of videos which is something mobile operators have not taken advantage of. Our value add is to work with operators to help get them addressing that audience. But today they are not doing a good job of monetizing that big audience for web video to the mobile device."??Pai said that vTap can interface with Facebook or other social networking site APIs to integrate people's profile into the mobile world.??"The science behind our services is very non trivial," Pai said. "It's not just an index and a simple search engine."??Currently Veveo says it has 500,000 users in either alpha, beta or some form of pre-launch usage. The company has attracted $28 million so far from VC, has 55 employees and was founded in late 2004.