Section A.1. 802.11ab WLAN Systems

A.1. 802.11a/b WLAN Systems

We start the derivations by revisiting the interference scenario considered in Figure 4-2, where a WLAN node is surrounded by several UWB transmitters in a two-dimensional setting. The scenario is reproduced here as Figure A-1. The inner circle defines the boundary of a UWB-free zone; that is, no UWB transmitters are closer to the victim than R_min. In between the inner and the outer circles (given by R_max), the UWB transmitters are distributed uniformly over the surface.

Figure A-1. The interference scenario considered: a WLAN node placed among UWB transmitters in communication with an access point

If we now let R_max tend to infinity, the victim receiver experiences a total interference power due to the UWB devices given by

Equation A-1

where r is the UWB density in users/m², P_UWB is the transmission power for each UWB device, l is the wavelength, and I(R_min, d₀) is a factor depending on the environment through d₀ and R_min. Details of the model can be found in [1]. From [1], the SINR at the victim receiver is defined by

Equation A-2

N₀ is the thermal noise (that is, we assume there is no neighboring channel interference), P_T denotes the transmit power at the access point, Const is the path loss as a function of distance, and UWB Interference represents the total received power from all the UWB devices around the victim receiver. Thus in dBm, we get

Equation A-3

Here we have defined M such that

Equation A-4

Therefore, any increase of M dB due to UWB interference will result in an equal decrease in the SINR. Hence, if we assume that the system can support a degradation of M dB in SINR, we can deduce the total amount of UWB interference corresponding to an M dB degradation such that

Equation A-5

We have also found a general value for UWB Interference as a function of the UWB transmitter density from R_min to infinity such that

Equation A-6

with

Equation A-7

and P_UWB the UWB transmit power (fixed by the maximum of the emission mask). So, we can find the maximum permissible UWB transmitter density r under the constraint that the SINR decreases not more than M dB such that

Equation A-8

Therefore, we can evaluate the permitted UWB density for different decreases in the SINR and estimate effects due to an introduction of UWB devices on IEEE 802.11a/b WLANs.