Dynamic RF matrix emulator
A dynamic RF matrix emulator uses digital switching to emulate the switching behavior of hundreds of wireless terminals. The emulator includes a switching matrix with channels formed between terminal pairs, digital front ends for coupling terminals digitally to the switching matrix, and a channel database having entries representing attenuation values which can be changed in time, the attenuation values correlated with movement of vehicles provided by a traffic simulator. Channel behavior is defined by temporal attenuation values obtained from the database. The digital switching is controlled through a digital communication protocol.
1. An apparatus for testing wireless terminals comprising:
a) a switching matrix coupled through a first plurality of M digital front end modules to a second plurality of N radio frequency (RF) terminals, the switching matrix having channels; and
b) a channel database for providing temporal channel attenuation data, wherein the channel database includes:
i. a storage element for storing database entries which represent channel attenuation values,
ii. a loading interface for enabling loading of the database entries into the storage element,
iii. a synchronization control element which serves as a timing element for controlling a current database entry, and
iv. a retrieval interface for providing a current database entry to a channel;
wherein the switching matrix, the terminals and the channel database are interconnected digitally and wherein the channel attenuation data is used for setting switching decisions.
2. The apparatus of claim 1 , wherein M is equal to N.
3. The apparatus of claim 2 , wherein a database entry is based on a current terminal location.
4. The apparatus of claim 1 wherein M is not equal to N.
5. The apparatus of claim 1 , wherein N>3.
6. The apparatus of claim 5 , wherein the digital connectivity protocol is the IEEE 802.3 protocol.
7. The apparatus of claim 1 , wherein the digital interconnection is enabled by use of a digital connectivity protocol.
8. The apparatus of claim 1 , wherein the terminals are mobile.
9. The apparatus of claim 1 , wherein a terminal includes a plurality of PHY modem chains.
10. An apparatus for testing wireless terminals comprising:
a) a switching matrix coupled through a first plurality of M digital front end modules to a second plurality of N radio frequency (RF) terminals, the switching matrix having channels, and including;
i. M input parameter extractor modules used for parsing incoming bit streams to obtain a transmitted power and data rate, and
ii. M output selector modules used for selecting data received by from transmitters and for digitally connecting the terminals, and
b) a channel database for providing temporal channel attenuation data;
wherein the switching matrix, the terminals and the channel database are interconnected digitally and wherein the channel attenuation data is used for setting switching decisions.
11. A method for testing wireless RF terminals comprising the steps of:
a) providing a dynamic RF matrix emulator which includes a switching matrix, a channel database and M digital front ends;
b) connecting N terminals through respective digital front ends across the switching matrix, a connection between two terminals forming a channel;
c) emulating the behavior of terminals through digital switching of the switching matrix to set switching decisions based on channel database entries; and
d) preparing the channel database offline, by:
i. using a driving simulator to provide locations of terminals and a surrounding map,
ii. calculating a channel model for each channel to obtain a current database entry, the entry including an attenuation value,
iii. quantizing the attenuation value to obtain a quantized attenuation value, and
iv. writing the quantized value to a storage element in the channel database.
12. The method of claim 11 , wherein the step of emulating includes providing temporally changing attenuation values to a channel.
13. The method of claim 11 , wherein the quantizing includes using a maximal quantization step less than half the minimum sensitivity of a terminal PHY modem.
14. A method for testing wireless RF terminals comprising the steps of:
a) providing a dynamic RF matrix emulator which includes a switching matrix, a channel database and M digital front ends;
b) connecting N terminals through respective digital front ends across the switching matrix, a connection between two terminals forming a channel; and
c) emulating the behavior of terminals through digital switching of the switching matrix to set switching decisions, wherein the step of emulating includes identifying terminals with a winner transmitter and a runner up transmitter, and comparing a difference in receive powers of the winner and runner up transmitters with a threshold to determine a switching decision.