Peaceful coexistence
By using Wi-Fi and Bluetooth silicon from CSR, users gain access to pioneering solutions for coexistence between radios.

Bluetooth has the AFH (adaptive frequency hopping) mechanism, which protects Wi-Fi by hopping around the core Wi-Fi channel in the frequency domain. However, this only works well when the antennas are separated by a reasonable distance.  Developers co-locating both functions inside a dual-mode cellphone have to contend with the problem of 'front-end overloading' as well. 

Front-end overloading is caused mainly by the higher transmission power levels of Wi-Fi, which - when combined with the proximity the embedded system imposes - are enough to saturate or de-sensitize the front end of the Bluetooth RF chain. Vice versa, Bluetooth can cause this same effect on the Wi-Fi front end.  Co-ordination using time domain multiplexing (TDM) between the two protocols - also known as Activity Signalling - is required to overcome this, and several proprietary schemes have been devised. 

CSR's Bluetooth devices such as the EDR-equipped BlueCore4 or BlueCore5-FM support all common coexistence measures developed by Wi-Fi silicon vendors. However, as CSR manufactures both Bluetooth and Wi-Fi devices, it's been possible to include further optimization measures. These additions are necessary because even when current protection techniques are utilised, coexistence issues remain. Take the example of someone using Bluetooth for voice communication while also surfing the web. The synchronous Bluetooth SCO connection will be disrupted by the packet reception acknowledgements that Wi-Fi is forced to transmit.

In this and other instances, users who build dual-mode handsets using BlueCore and UniFi are assured of seamless coexistence in foreseeable operating scenarios thanks to CSR's unique measures. For example, CSR's coexistence demonstrations include a VoIP call over a Wi-Fi link using a Bluetooth headset; streaming stereo music to Bluetooth headphones while simultaneously browsing the internet or downloading an MP3 file; receiving a phone call over a Bluetooth headset while surfing the internet; and simultaneous transfer of files over Bluetooth and Wi-Fi links. The TDM and proprietary measures built into the UniFi device (with UMA-compliant 17 dBm radio frequency output power) ensure that synchronous Bluetooth HV3 packets do not cause interference.  

In head-to-head comparisons, when both Wi-Fi and Bluetooth are used concurrently, data throughput for UniVox Mobile is significantly faster than competitive offerings on the market. By providing both hardware and software elements customers can benefit from fast time to market for dual mode products.

Contact your local CSR office to find out more.