Combining unicast & broadcastWireless technologies are always more capacity limited than desired. Mostly this is due to missing frequency spectrum. Also the availability of standard receivers supporting wider spectrum ranges is limited. On the other hand several services - like IPTV - require only a narrow band client-to-server connection (uplink).
Our hybrid network approaches therefore combines unicast and broadcast technologies based on standard devices - as well on the client side as on network side. This approach can be realized with any broadcast and unicast technology as long as IP-streams are supported.
MAIKE - WiMAX & DVB-T
Initially our approach for combination of unicast and broadcast networks has been developed based on WiMAX (IEEE 802.16-2004) and DVB-T within the project "MAIKE" (Mobile assistence systems, in particular in e-learning scenarios). Here, like in many similar scenarios, more capacity was needed to transmit video data in near-real-time. Since the same stream has to be provided to many recipients it was efficient to "broadcast" such data.
In project MAIKE brown-iposs realized with its partners from University of Rostock and a local WiMAX-provider a complete WiMAX+DVB-T-network infrastructure. A particular focus of brown-iposs' work in this approach was setting-up the traffic split and merging on client & server side for sending the IP-stream over the best suited technology.
In the meantime this approach has been implemented also with other technologies including a pure WiFi / WiFi - approach. The project MAIKE was partly funded by the Ministry of Economic Affairs of Mecklenburg-Western Pomerania.
To realize a hybrid network special clients are required which are able to communicate with the network and to forward the joint data stream received from the network to local recipients. brown-iposs developed a special CPE (customer premises equipment) - called Stream Aggregator (StA) - for this task, based on an embedded Linux-system. It is interfacing with of-the-shelf receivers like DVB-T sticks and WiMAX-CPEs.
It is also possible to build an StA as a smartphone-app for Android
to support real mobility. However currently this lacks on widely
available smartphones in the market who support broadcast
technologies like DVB-T or DVB-H.
ApplicationsHybrid networks are best suited for fixed access scenarios. In such scenarios it is easy to adjust antennas to both radio technologies, stream aggregators can be integrated in local CPEs which are required anyway. However there are lots of applications which may be based on fixed-access nodes. E.g. the backhauling of hotspots in a City-WiFi network can be done with fixed-access links. Therefore brown-iposs integrated the hybrid network technology in its Integrated Radio Masts.
The technology developed for Hybrid networks can be used also in adjacent apllication areas. Providing internet in a stadium or crowded location is only feasible if the traffic is handled in a very smart way. Using multicast for transmitting video data e.g. is a must in a crowded place. However this needs special protection mechanism to ensure the transmitting quality. The approach developed for Hybrid networks is used therfore also as a Video Quality Enhancement system in our MOTIware Connected Crowd solution.