A processing module for a receiver device configured to provide for processing of a signal received by the receiver device from a transmitter device, the signal comprising a preamble comprising a plurality of repeating, predetermined synchronization symbols known to the receiver device and the transmitter device and a secure training sequence, the secure training sequence divided into a plurality of time spaced blocks, the secure training sequence comprising a non-repeating pattern of symbols, and wherein one of: a) at least a first block is transmitted from a first antenna and a second block is transmitted from a different second antenna of the transmitter device; b) at least a first block is received by a first antenna and a second block is received by a different second antenna of the receiver device; wherein the processing module is configured to: based on the plurality of repeating, predetermined synchronization symbols of the signal, provide for determination of a phase of a carrier wave of the signal received at the first antenna of the receiver device or transmitted from a first antenna of the transmitter device; derive, using a Cryptographically Secure Pseudo-Random Number Generator, a secure training sequence corresponding to the secure training sequence of the signal based on predetermined secure information known to both the transmitter and receiver device, the secure information comprising one or more of an agreed symbol sequence and an agreed reference for generation of such a symbol sequence agreed between the transmitter device and the receiver device, the secure training sequence comprising a non-repeating pattern of symbols; perform cross correlation between the first block (1603, 1605) from the first antenna and a first part of the derived secure training sequence to obtain a first phase marker defining a phase of the signal from the first antenna relative to the determined phase of the carrier wave; perform cross correlation between the second block (1604, 1606) from the second antenna and a second part of the derived secure training sequence to obtain a second phase marker defining a phase of the signal from the second antenna relative to the determined phase of the carrier wave; based on the first phase marker and the second phase marker defining a phase difference of the signal between the first and second antennas and a known spacing of the first antenna relative to the second antenna, determine an angle of arrival of the signal relative to the receiver device. a) at least a first block is transmitted from a first antenna and a second block is transmitted from a different second antenna of the transmitter device; b) at least a first block is received by a first antenna and a second block is received by a different second antenna of the receiver device; based on the plurality of repeating, predetermined synchronization symbols of the signal, provide for determination of a phase of a carrier wave of the signal received at the first antenna of the receiver device or transmitted from a first antenna of the transmitter device; derive, using a Cryptographically Secure Pseudo-Random Number Generator, a secure training sequence corresponding to the secure training sequence of the signal based on predetermined secure information known to both the transmitter and receiver device, the secure information comprising one or more of an agreed symbol sequence and an agreed reference for generation of such a symbol sequence agreed between the transmitter device and the receiver device, the secure training sequence comprising a non-repeating pattern of symbols; perform cross correlation between the first block (1603, 1605) from the first antenna and a first part of the derived secure training sequence to obtain a first phase marker defining a phase of the signal from the first antenna relative to the determined phase of the carrier wave; perform cross correlation between the second block (1604, 1606) from the second antenna and a second part of the derived secure training sequence to obtain a second phase marker defining a phase of the signal from the second antenna relative to the determined phase of the carrier wave; based on the first phase marker and the second phase marker defining a phase difference of the signal between the first and second antennas and a known spacing of the first antenna relative to the second antenna, determine an angle of arrival of the signal relative to the receiver device.