Conformity Magazine - January 2009 - (Page 28) Design and Regulatory Issues for Collocated Transceivers by Inam Rahim, Intelligent Mechatronic Systems Inc. he easy availability of low power unlicensed wireless modular transceivers in the market, such as Bluetooth, WiFi, cellular modems and many short-range devices (SRDs), has helped in creation of numerous new applications. Some applications tend to use more than one transceiver in their design, and the transceivers are often placed in close proximity to one another. This type of usage is called collocation of transceivers. For a single low power transceiver in a device, rules on power limit and emissions have been clearly described by regulatory bodies in North America and the European Union (EU). There can be small variations in the limits and other parameters in two regions. However, if the device function requires more than one transceiver within close proximity, rules to regulate such a design are not clear. North American regulatory bodies do not even talk about such a scenario. In fact, until a few years ago, nobody would have thought that industry would come up with devices and functions using multiple transceivers in close proximity (and often on the same PCB!) which actually work. In North America, FCC-15 sub-part C [2] and Canadian RSS-210 [5] regulate exempt wireless devices. But the regulations do not discuss the collocation of transceivers. However, the Federal Communications Commission (FCC) prohibits collocation of transmitters in the “grant note” when a certification is issued to any such device, which is a source of confusion. 28 Conformity JAnUAry 2009 © Marius Hainal | Dreamstime.com T In the EU, we have ETSI regulations TR 102 070-1 [9] and TR 102 070-2 [10], which specify various modes of multiple transceivers used in close proximity, and the testing requirements for combined product as well as the individual parts. This article looks at the radio collocation phenomenon and its implications from both engineering and regulatory viewpoints. How are such designs treated in the existing spectral control regulations? Or, do any regulations exist for such multi transceiver devices? The technical problems of collocation, and the current regulations in both North America and the EU, are also discussed. Collocation of Transceivers - The Engineering Sense In many applications, collocation of a few transceivers is a desirable feature. In some situations, it is a must to have several transceivers working in close proximity (e.g., in an air traffic control tower, where multiple communications must be carried out simultaneously). Creating such a working environment is not easy, since all the communications are asynchronous (transmit or receive of any two transceivers is not synchronized), and it is not easy or desirable to make them synchronous. The important difference here is that transceivers collocated within a single piece of equipment or single device (or PCB) are not meant to communicate with one another, wirelessly. http://www.Dreamstime.com
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