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stds-80220-ch-models: New channel measurements

Dear All,

I want to describe the measurement capability and measurements that we 
are planning to do this year in support of MIMO technology development.


As part of a program to support the development of spectrally efficient 
technologies, in particular, MIMO technology, the Institute for 
Telecommunication Sciences (ITS) is planning to make mobile, MIMO 
channel measurements in 2004. To maximize the value of these 
measurements, ITS will accept input from IEEE 802.20 participants and 
other interested parties regarding how these measurements should be 
made to provide results useful in the development of the 802.20 
standards and mobile, broadband data communications in general.

ITS is a Federal research laboratory housed in the National 
Telecommunications and Information Administration and located in 
Boulder, Colorado. ITS is a central resource for telecommunications 
research for Government and industry and has made major contributions 
to propagation modeling and measurements since the second world 
war.  Experienced, internationally recognized experts in radio channel 
modeling and measurements as well as state-of-the-art equipment will be 
utilized in this research effort.


As currently configured, the measurement system transmits up to 16 
signals at 2250 MHz, which are received on up to 4 receivers. By using 
BPSK modulation and pseudo-random noise (PN) binary codes, the 
complex-valued impulse response of each element in the transmission 
matrix can be measured. This is done by digitally sampling the IF of 
each receiver and cross correlating the samples with a sampled version 
of each of the transmitted signals.

Currently each transmitter has an output power of 24 dBm. A single 
511-bit PN code word is used at equally spaced delays for each transmit 
channel. The code word is clocked at 10 MHz. Thus, it takes 51.1 
microseconds to transmit the code word, which then repeats. Each 
channel’s code word is delayed 3.2 microseconds from the previous 
channel limiting the time delay measurement range to 3.2 
microseconds. The transmitted spectrum falls off from the carrier 
frequency as the sinc function with the first nulls on both sides 
separated by 20 MHz. The receivers sample at 40 MHz with 14-bit 

The configuration of this system can be changed, if necessary, in a 
number of ways, including.

1.	A different carrier frequency could be used.
2.	The number of received channels can be increased beyond 4.
3.	Longer or shorter PN code words can be used.
4.	OFDM signals can be transmitted instead of a single BPSK carrier.
5.	The code word can be clocked at up to 20 MHz.

Data collection is currently done in two modes. In the burst mode, the 
received signal is sampled for the duration of one code word. This is 
repeated up to 256 times with a spacing of from 102.2 microseconds to 
many milliseconds. The spacing determines the maximum Doppler frequency 
that can be unambiguously measured. A burst measurement can be recorded 
each second or spaced further apart.

 In the continuous measurement mode, all receiver signals are sampled 
for the duration of one code word. This is repeated continuously as 
fast as every 400 microseconds, until the disk is full (30 GB).


 The current plan for the measurements this year is to transmit at 2250 
MHz from 4 base-station like antennas, each BPSK modulated at a 10 MHz 
chip rate using one repeating, 511-bit, PN code word, with each of the 
four signals separated by a delay of 128 bits or 12.8 microseconds.

 Four receiving antennas representative of the type that may be used on 
a vehicle and of the type that may be used on a handheld device will be 
used at the mobile terminal. The signal from each of the 4 receiving 
antennas will be digitally sampled at 40 M-samples/second (14-bit 
resolution) using the burst-sampling mode described above. The spacing 
between the waveform samples will be chosen to provide better than a 
Nyquist-frequency sampling rate for the maximum possible Doppler 
frequency during the measurement.

 Outdoor measurements will be made in downtown Denver, an urban 
area. (Subsequent measurements may be made with the antennas in several 
different physical configurations. This would enable the measurement of 
MIMO capacity for various antenna diversity schemes involving various 
antenna spacings and polarizations.)

 The outdoor measurements will utilize a fixed base station with a 
height of 17m and a mobile measurement van.  (Future measurements may 
be made indoors or outdoor-to-indoor.

 The currently planned processing of the measurement data is as 
follows. Each set of MIMO waveform samples (51.1 microseconds long), 
will be cross-correlated in post processing with a digitally sampled 
version of the transmitted signal producing the complex values (phase 
and amplitude) of the elements of the MIMO transmission matrix. The 
rank of each matrix will be computed. (Note: This can be done using a 
variety of combinations of numbers of transmit and receive antennas.)

The statistics of the rank and its time dynamics (such as coherency 
time and distance) will be determined for each combination of path 
type, environment, and antenna diversity.


 Suggestions are welcome from individuals, and the 802.20 channel 
modeling group as a whole, of modifications to the measurement system, 
measurement plan, and data analysis that will provide more useful 
results. Unfortunately, I was not able to attend the Vancouver meeting, 
but I plan to attend the March meeting.

To save time, I will respond to questions and/or suggestions at any 
time before the next meeting.  I can be reached at 303-497-5474 or

Thank you very much for your help.


Kenneth C. Allen							*
Wireless Program Leader						*
NTIA/Institute for Telecommunication Sciences	*
325 Broadway								*
Boulder, CO  80305							*
Phone:  303-497-5474						*
Fax:  303-497-3680							*
E-mail:					*