US 9,426,010 B1Granted

Adaptive symbol transition method for OFDM-based cognitive radio systems

AssigneeUniversity of South Florida

InventorsHisham A. Mahmoud, Huseyin Arslan

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Abstract

Modulated orthogonal frequency division multiplexing (OFDM) subcarriers generate high sidelobes, resulting in adjacent channel interference (ACI). Current sidelobe suppression techniques, such as inserting guard intervals or cancellation carrier bands, diminish the useful radio spectrum or consume significant wireless device resources. Disclosed is a method of suppressing sidelobes through adding an adaptive extension to OFDM symbols that is calculated to avoid ACI while keeping power consumption to low levels. Bandwidth and user location information are collected by a cognitive radio an utilized to determine the extension used. The method significantly reduces ACI to other bands and reduces the required guard bands, opening the radio spectrum to more efficient use.

Claims14

Dependent claims

A system for reducing orthogonal frequency-division multiplexing symbol interference, the system comprising:

an antenna adapted to receive and transmit signals on a plurality of radio wavelengths;
a cognitive radio engine to receive one or more signals from the antenna and to identify a licensed user location and bandwidth information from the signals received from the antenna;
a modulator to receive encoded data from a cognitive radio user and to modulate the encoded data to generate modulated encoded data;
an orthogonal frequency-division multiplexing transformer in electrical communication with the modulator, the orthogonal frequency-division multiplexing transformer to receive the modulated encoded data from the modulator and to transform the modulated encoded data to time domain orthogonal frequency-division multiplexing symbols;
an interference suppression module comprising:
a first input to receive the time domain orthogonal frequency-division multiplexing symbols from the orthogonal frequency-division multiplexing transformer;
a second input to receive the licensed user location and bandwidth information from the cognitive radio engine;
a signal extension module comprising logic to select a symbol extension for the time domain orthogonal frequency-division multiplexing symbols using a linear least squares with quadratic constraint of the licensed user location and bandwidth information;
an adaptive symbol transition module comprising logic to extend the time domain orthogonal frequency-division multiplexing symbols by generating a minimum transition symbol based on the symbol extension selected by the signal extension module the licensed user location and bandwidth information, the adaptive symbol transition module further configured to append the minimum transition symbol to the time domain orthogonal frequency-division multiplexing symbols to generate symbol extended time domain orthogonal frequency-division multiplexing symbols;
and
an output adapted to deliver the symbol extended time domain orthogonal frequency-division multiplexing symbols.

8 more elements

One or more non-transitory computer-readable media having computer-executable instructions for performing a method of running a software program on a computing device, the computing device operating under an operating system, the method including issuing instructions from the software program comprising:

obtaining a set of sample information for at least one licensed user operating in one or more licensed user bands, the set of sample information including at least one of a licensed user location, a licensed user bandwidth, a licensed user frequency subcarrier, or a licensed user center frequency;
performing an adaptive symbol transition function, including:
providing a first time domain symbol of an orthogonal frequency-division multiplexing symbol;
providing a second time domain symbol of the orthogonal frequency-division multiplexing symbol;
adding the first time domain symbol and the second time domain symbol together obtain a transition symbol;
applying a function to generate a minimum transition symbol using an adaptive symbol transition module, the function being:
A
(
m
)
=
arg
⁢
⁢
min
A
(
m
)
⁢

F
I
⁢
A
(
m
)
+
I
L

2
,
where A(m) is the minimum transition symbol, FI is a subset of sample information for at least one licensed user, IL is interference to the licensed user;
appending the minimum transition symbol to an end of the first time domain symbol of the transition symbol;
and
appending the second time domain symbol of the transition symbol to the minimum transition symbol to form transitioned time domain symbols, wherein the transitioned time domain symbols reduce interference by suppressing orthogonal frequency-division multiplexing sidelobes.

35 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/746,151Filed 22 Jun 2015 · continuation in part
Priority: 21 Nov 2007
Granted: 23 Aug 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H04L 27/26265
Arrangements specific to the transmitter only: arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral…
H04B 15/00
Suppression or limitation of noise or interference
H04L 25/03834
Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties: using pulse shaping
H04L 27/0006
Modulated-carrier systems: assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in…

Family

Application60/989,487Us provisional application · filed 21 Nov 2007
Application12/275,721Parent of this continuation-in-part · filed 21 Nov 2008
Application14/064,790Parent of this continuation-in-part · filed 28 Oct 2013
US 8,571,136 B1Parent of this continuation-in-part · filed 29 Oct 2013
US 9,106,324 B1Parent of this continuation-in-part
US 9,426,010 B1This patent

From the US filing history. Foreign family members aren’t listed.