Wireless communications networks

1. A method of mitigating start-of-packet interference in a millimetre waveband wireless mesh communications network which comprises: a first plurality of network node devices each having a transceiver unit which includes a beamforming antenna device, and a second plurality of millimetre waveband wireless communications links each of which interconnects a respective pair of the transceiver units of the network node devices, the method comprising:

allocating respective baseband centre frequencies to pairs of transceivers of the network node devices, which baseband centre frequencies are for use with respective communications links of the network, each such allocated baseband centre frequency being offset from at least one other allocated baseband centre frequency by a respective predetermined offset amount; and

at a first transceiver of a selected pair of transceivers, encoding a data packet using an encoding signal having the baseband centre frequency allocated to the selected pair of transceivers, to generate an encoded signal;

wherein at least some data packets transmitted in the mesh communications network comprise detection data sequences for detection of the data packets by a receiver, and the respective predetermined offset amount is such that a correlation between a detection data sequence and version of the detection data sequence that is frequency offset by the respective predetermined offset is below a detection threshold for the detection data sequence.

2. The method of claim 1 , wherein the predetermined offset amount is less than a tenth of a bandwidth of the communication links.

3. The method of 1 , wherein the communication links uses single carrier modulation.

4. The method of claim 1 , further comprising: at the first transceiver modulating a radio frequency carrier signal with the encoded signal to generate a transmission signal, the modulating applying a frequency translation of the encoded signal by a value equal to a carrier frequency being a centre frequency of a frequency channel of the millimetre waveband wireless mesh communications network.

5. The method of claim 1 , further comprising at the first transceiver:

controlling a beamforming antenna device of the transceiver to enable transmission therefrom in a predetermined transmission direction; and

transmitting the transmission signal from the beamforming antenna device in the predetermined transmission direction.

6. The method of claim 1 , further comprising, at a second transceiver of the selected pair of transceivers:

receiving the transmission signal at the beamforming antenna of the second transceiver as a received signal;

demodulating the received signal with a radio frequency signal at the carrier frequency, to generate a received encoded signal; and

decoding the received encoded signal using a decoding signal having the baseband centre frequency allocated to the selected pair of transceivers.

7. The method of claim 1 , wherein the predetermined offset amount is less than a fifth of a symbol rate of the data packet.

8. The method of claim 1 , wherein the step of allocating respective baseband centre frequencies is performed at least partially by a central network resource of the communications network.

9. The method of claim 1 , wherein the step of allocating respective baseband centre frequencies is performed at least partially by a media access controller, MAC, of each network node device.

10. A millimetre waveband wireless mesh communications network comprising:

a first plurality of network node devices each having a transceiver unit which includes a beamforming antenna device;

a second plurality of millimetre waveband wireless communications links which interconnect respective pairs of transceiver units of the network node devices; and

a baseband centre frequency allocation unit operable to allocate respective baseband centre frequencies to pairs transceivers of the network node devices, which baseband centre frequencies are for use with respective communications links of the network, each such allocated baseband centre frequency being offset from at least one other allocated baseband centre frequency by a respective predetermined offset amount,

wherein a first transceiver of a selected pair of transceivers is operable to encode a data packet using an encoding signal having the baseband centre frequency allocated to the selected pair of transceivers, to generate an encoded signal; and

at least some data packets transmitted in the mesh communications network comprise detection data sequences for detection of the data packets by a receiver, and the respective predetermined offset amount is such that a correlation between a detection data sequence and version of the detection data sequence that is frequency offset by the respective predetermined offset is below a detection threshold for the detection data sequence.

11. The millimetre waveband wireless mesh communications network of claim 10 , wherein the predetermined offset amount is less than a tenth of a bandwidth of the communication links.

12. The millimetre waveband wireless mesh communication network of claim 10 , wherein the first transceiver of the selected pair of transceivers is further operable to modulate a radio frequency carrier signal with the encoded signal, to generate a transmission signal, to control a beamforming antenna device of the transceiver to enable transmission therefrom in a predetermined transmission direction; and to transmit the transmission signal from the beamforming antenna device in the predetermined transmission direction.

13. The millimetre waveband wireless mesh communication network of claim 10 , wherein a second transceiver of the selected pair of transceivers is operable to receive such a transmission signal at the beamforming antenna of the second transceiver as a received signal, to demodulate such a received signal with a radio frequency signal at the carrier frequency, to generate a received encoded signal, and to decode such a received encoded signal using a decoding signal having the baseband centre frequency allocated to the selected pair of transceivers.

14. The millimetre waveband wireless mesh communication network of claim 10 , wherein the baseband centre frequency allocation unit is at least partially provided by a central network resource.