WiMAX based point to multipoint system operating in frequencies below 1 GHz

• US 8,098,604 B2
• Filed: 04/20/2009
• Issued: 01/17/2012
• Est. Priority Date: 04/20/2008
• Status: Active Grant

• Current Assignee: Ondas Networks Inc.
• Original Assignee: Full Spectrum Inc.
• Inventors: Shahar, Menashe
• Primary Examiner(s): Vu, Huy
• Assistant Examiner(s): Renner, Brandon
• Application Number:
  US12/426,697
• Publication Number:
  US 20100265851A1
• Time in Patent Office: 1,002 Days
• Field of Search: 370/378
• US Class Current: 370/310
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 88/00 Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices

Abstract

A system for the delivery of high speed data mission critical, private broadband wireless networks based on a modified version of the ieee802.16e-2005 standard and subsequent versions of this standard referred to, known as “mobile WiMAX”. The system comprises a plurality of base stations, each of said base stations covering at least one sector, which maintain two-way data communication, with a plurality of mobile stations and fixed subscriber stations in its serving area, over licensed frequency bands below 1 GHz in accordance with the mobile WiMAX standard. The mobile WiMAX air interface standard (ieee802.16e) is modified for channel sizes below 1.25 MHz.

Claims

1. A point to multipoint wireless system comprising:

a router hub;

a plurality of base stations, each of said base stations covering at least one sector; and

a plurality of mobile stations and fixed subscriber stations,

wherein each of said plurality of base stations maintains two-way data communication with said plurality of mobile stations and fixed subscriber stations in its serving area, over licensed frequency bands below 1 GHz in accordance with the mobile WiMAX air interface standard (ieee802.16e),

wherein the mobile WiMAX air interface standard (ieee802.16e) is modified for channel sizes below 1.25 MHz, and

wherein the PHY (physical) Layer of each of said plurality of base stations and each of said plurality of mobile and subscriber stations is configured to support channel sizes having a bandwidth less than 1.25 MHz by scaling down the sub-carrier frequency spacing in a linear proportion to the standard mobile WiMAX 128 FFT configuration designed for a 1.25 MHz wide channel.

2. The system according to claim 1, further comprising a base station controller in communication with said router hub.

3. The system according to claim 1, wherein said frequency bands have a range of frequencies from 40 MHz to 1 GHz.

4. The system according to claim 1, wherein said two-way data communication utilizes Time Division Duplexing (TDD) operation.

5. The system according to claim 1, wherein each of said plurality of base stations and each of said plurality of mobile stations comprises:

a baseband processor module in communication with an analog front end module, said baseband processor module comprising;

a general purpose processor;

a general purpose DSP (Digital signal processor);

a general purpose FPGA (field-programmable gate array); and

a GPS module.

6. The system according to claim 5, wherein said baseband processor module has a bank of digital filters implemented in the FPGA, each filter of said bank of digital filters configured to support a specific channel size and specific downlink and uplink permutations and specific FCC spectral mask, in accordance with the mobile WiMAX standard.

7. The system according to claim 5, wherein the analog front end is configured, during transmission, to perform the steps of:

reception of digital I and Q from the Baseband Processor Digital to Analog conversion;

frequency up-conversion from baseband to a pre-determined IF frequency and then down-conversion to the RF frequency;

amplification to the TX power level using a configurable attenuator, wherein the TX power level is configured manually by the operator at the base station and configured automatically at the mobile station using the mobile WiMAX ranging process;

filtering to suppress out of channel and out of band interference;

Digital Pre-Distortion (DPD) equalization to attenuate inter-modulation products generated as a result of Power Amplifier non-linearity thereby to reduce transmit power backoff requirements; and

feeding at least one signal to at least one antenna) through a T/R switch to support TDD operation, wherein during the transmit phase of the TDD frame, the T/R switch is in the Transmit state and the transmit signal is returned to the receive path through a coupler,

and wherein the transmit signal is returned over the receive path as a feedback signal for the DPD.

8. The system according to claim 7, wherein the analog front end is configured, while receiving, to perform the steps of:

RF filtering to protect the LNAs;

Reception of the RF signal from the antenna through the T/R switch, when in the receive state;

Low Noise Amplification;

frequency up-conversion from the RF frequency to a pre-determined IF frequency, IF filtering using a SAW filter bank, Automatic Gain Control (AGC) amplification and down-conversion and demodulation into analog I and Q signals;

analog filtering of analog I and Q by means of a programmable analog filter; and

analog to digital conversion of I and Q and delivery to the baseband processor module.

9. The system according to claim 1, wherein the available bandwidth is reused in each sector in a tower site.

10. The system according to claim 9, wherein each sector in a tower site operates over distinct sub-channels, wherein any two sectors in the tower site do not employ the same sub-channels.

11. The system according to claim 10, wherein the analog front end module at each of said base stations and each of said plurality of mobile stations is configured to deliver all sub-channels within the channel to the baseband processor module, wherein the baseband processor module only processes the sub-channels that are utilized in the respective sector.

12. The system according to claim 11, wherein each of said plurality of base stations utilizes a Fractional Frequency Reuse (FFR) scheme, said FFR comprising:

a DL (Downlink) MAP message having two PUSC (Partially Use of Sub Carrier) zones and an UL (Uplink) MAP message having two PUSC zones;

wherein the first PUSC zone in the DL MAP message and in the UL MAP message are allocated all the sub-channels;

the second PUSC zone in the DL MAP and in the UL MAP are allocated distinct sub-channels, which have not been allocated in the second zone in other sectors at the same tower site; and

wherein each mobile station is allocated transmit opportunities in the first or second zone, depending on its instantaneous Carrier to Interference and Noise Ratio (CINR).

13. The system according to claim 5, wherein said baseband processor module further comprises a RS232 interface configured to interface to legacy Supervision Control and Data Acquisition (SCADA) devices, wherein a non-standard Service Specific Convergence Sub-layer is configured to encapsulate the legacy SCADA protocol over the mobile WiMAX air interface protocol.

14. The system according to claim 1, wherein the sub-carrier frequency spacing (Δ

f) is reduced in accordance with the formula;

Δ

f=(BW/1.25 MHz)*10.94 KHz, The Useful Symbol time (Tb) will be increased in accordance with the formula;

Tb=1/Δ

f=1/((BW/1.25 MHz)*10.94 KHz), the Cyclic Prefix (Tg) will be increased in accordance with the formula;

Tg=Tb/8 and the Total OFDMA Symbol Time (Ts) will be increased to Ts=Tg+Tb.

15. The system according to claim 1, wherein the number of sub-carriers is reduced in accordance with the formula:

N=floor (BW/10.94 KHz).

16. The system according to claim 4, wherein the each TDD frame comprises at least 47 OFDMA symbols.