EDNE December 2012 - (Page 36)

S TANDARD 5MHz BLUETO OTH S MSC WIFI T HRO UG HP UT Yes Yes Yes Yes POW E R ( R AN K ) 4 2 1 3 U B I Q U I Ty No Yes No Yes R AN G E Single room Multi-room (marginally) Single room Multi-room Table 1: A summary of the major wireless standards available to the wireless speaker designer, which best meets your needs? Figure 3: There are many trade-offs to be made; efficiency vs. quality vs. ease of use. The SMSC Kleer standard is highly efficient, and delivers very high quality but requires a dongle to connect to a smart phone. 2200-mAh Li-ion battery and our stereo amplifier gave approximately 30 hours of normal playback. A module based on our mono amplifier, the SMSC Kleer wireless chip and a 1.2-V, 3000mAh AA battery achieved just over 40 hours of typical playback, which is comparable with the results from Bluetooth . WiFi, however, consumes significantly more power than either of these two standards. The only commercially available speaker efficient enough to run Apple’s AirPlay standard and be battery powered, was launched earlier this year. This uses the same HiWave stereo amplifier as the Bluetooth test, with a 5200 mAh Li-polymer battery and gives 10 hours of playback. It’s important to note that power consumption varies greatly according to the software stack. Clever software can make a great deal of difference. Ozmo Devices, for example, has created an ultra low power variant of WiFi that, the company says, is suitable for wireless speakers. We have not tested the 5 GHz chips, however these have been created for “prosumer” audio, mains powered equipment and consume significantly more power. INTERFERENCE AND RANGE Consumers also demand enough range to move out of a room with their phones. Anyone who has ever tried to transfer a picture or music file from a phone to a laptop using Bluetooth will know that whilst you can do this in separate rooms, the transfer rate declines noticeably if you move to the opposite corner of the house. WiFi, however, is particularly effective at going through walls, allowing the system to continue playing to friends when the owner of the “host” phone leaves the room. The 5GHz band provides greater bandwidth than either WiFi or Bluetooth, but these signals tend to have more trouble penetrating solid objects such as walls and floors and the technology is often described as more of a cable replacement technology. EASE OF USE It’s an overly used term but plug-and-play capability is essential for all technologies in order to create mass-market appeal. People want to be able to switch on a device and have it work instantly, with configuration happening automatically. Bluetooth has been standard on almost all new laptops, mobile phones and tablets for around 10 years. And a similar story is true for WiFi. For the limited number of PCs without Bluetooth, dongles are exceptionally cheap. This means there is no requirement to carry (and potentially lose) additional hardware. Whilst Summit’s 5 GHz wireless chips are being integrated into home theatre systems, they are not cheap, with the only two commercially available systems being made by Aperion and retailing at $2499 and $2999 respectively. CONCLUSIONS Whilst they are not seeking to achieve prosumer quality, and even though many are content with the free 96 kbps Spotify streams, consumers will not accept problems caused by a wireless network, whether this appears in the form of exceptionally short range, or of interference. Whilst it’s true that the 2.4 GHz frequency-band, within which both Bluetooth and WiFi operate, is both crowded and prone to interference, it can, and does, suffice for the transmission of audio stored on a phone or PC. In an article entitled 20 Myths of WiFi Interference, Cisco lists microwave ovens, cordless phones, Bluetooth devices, wireless video cameras, outdoor microwave links, wireless game controllers, Zigbee devices, fluorescent lights, WiMAX, and even bad electrical connections as sources of interference for 802.11 WiFi networks. Although both distance and interference will affect data transmission on a network, and research into WiFi shows that data rates can drop by 30% compared with fixed solutions, the quality of experience doesn’t always degrade and the 2.4 GHz band is good enough for the transmission of 320 kbps audio files streamed from a mobile phone or PC to battery-powered wireless speaker. 36 EDN EUROPE | december 2012 Consumers now prefer to store audio in digital formats, on several devices and in the cloud. And they want to listen to this audio from proper speakers, that deliver HiFi sound quality, rather than those built into their phone, PC or tablet. Low quiescent power amplifier ICs enable battery life to be extended significantly and enable up 40 hours of playback from a single AA battery or 6-plus months from larger batteries. For the present, the power consumption and ubiquity of Bluetooth suggests it has the edge as the wireless channel of choice: however, WiFi is fast catching up and as smart TVs – which only have WiFi chipsets – become more commonplace, and power consumption drops, WiFi looks set to eventually match, or even exceed this potential. Ultimately, as all major wireless standards are capable of delivering the required bandwidth, we’ll see the key system differentiators being battery life, ease of use and cost. James Lewis is CEO of HiWave Technologies, a UK based firm that designs and sells ultra-efficient, wireless-standard agnostic amplifier ICs, full audio range speaker drivers and third generation (position specific response) haptic feedback chips and actuators. www.edn-europe.com http://www.cclonline.com/product/55592/BT-USB-M2/Bluetooth/Dynamode-BT-USB-M2-Compact-Bluetooth-USB-Adaptor/NET0186/ http://www.cisco.com/en/US/prod/collateral/wireless/ps9391/ps9393/ps9394/prod_white_paper0900aecd807395a9_ns736_Networking_Solutions_White_Paper.html http://www.edn-europe.com

Table of Contents for the Digital Edition of EDNE December 2012

Cover
Contents
Texas Instruments Europe
Microchip
Digi-Key
Masthead
EDN comment
Pulse
Digi-Key
Baker’s Best
Embedded World 2013
Test & Measurement World
Rohde & Schwarz
Digi-Key
Squeezing the most from battery cells with a switched-mode pump
Signal integrity
Processor architectures : one to rule them all ?
Digi-Key
Mechatronics in Design
Advances in wireless speaker performance and technology
Design Ideas
Teardown; the ultimate Consumer Product ?
Product roundup
Tales from the Cube

EDNE December 2012