RF propagation characteristics of in-cabin CDMA mobile phone networks

Towards the goal of evaluating compatibility between passenger transmitting portable electronic devices (T-PEDs) and potential interference victims, such as avionics receivers and terrestrial mobile phone networks, we conducted an investigation onboard a Boeing MD-90 aircraft using CDMA handsets. The objectives of these tests were: 1) to determine a multiple equipment factor (MEF) to create a simulated signal source with RF energy equivalent to multiple T-PEDs inside the cabin; 2) to verify the hypothesis that MEF can be determined analytically using an accurate path loss model and the spatial distribution of T-PEDs within the cabin; 3) to evaluate external RF signal leakage from in-cabin mobile networks to assess potential interference to terrestrial mobile phone networks; 4) to evaluate passenger effects on RF propagation within the aircraft cabin. The aircraft cabin was equipped with picocell equipment capable of supporting 100 simultaneous CDMA mobile phone calls. 100 commercial-grade CDMA handsets were distributed evenly throughout the cabin. All handsets were configured for one of two scenarios: 1) manual full-power operation (representing the worst case); or 2) power-controlled communication with the picocell, where the phone is dynamically commanded to transmit the minimum power necessary to maintain the digital link. In each of these configurations, received power was measured mid-aisle along the length of the cabin, as well as external to the aircraft to a range of 1 km. Major findings were: 1) At mid-aisle, typical MEF for 100 phones was 9 dB; 2) MEF was accurately predicted from a empirically-derived path loss model and the known distribution of devices within the cabin; 3) Compared to full-power operation, cumulative power from 100 phones was reduced by approximately 60 dB when in communication with an onboard picocell; 4) Under picocell control, cumulative signal power from 100 phones was not observable beyond approximately 200 meters from the aircraft; 5) A handset outside the aircraft was unable to acquire the picocell signal beyond approximately 500 meters; 6) Each passenger standing in the aisle produced 0.5 to 1.0 dB of additional path loss along the length of the cabin.