A symbol transmitting method, including: determining N+1 transmission symbols s.sub.0, s.sub.1, s.sub.2, . . . , s.sub.N, according to a reference symbol and (M1+M2)*N bits, where 0, 1, 2, . . . , N are indices of the N+1 transmission symbols, s.sub.0 is a reference symbol, an amplitude of a transmission symbol with index n is determined according to M1 bits, a phase of the transmission symbol with index n is determined according to a phase of a transmission symbol with index n?1 and M2 bits, M1 is an integer greater than or equal to 1. M2 is an integer greater than or equal to 1, N is an integer greater than or equal to 1, 1?n?N, and n is an integer; and transmitting the N+1 transmission symbols.

Communication devices and a method of providing secure electronic content are general described. A plainmodulation containing user content is encrypted using a modulation key to form a ciphermodulation having a different magnitude and/or phase than the plainmodulation. Symbol representations of the plainmodulation and ciphermodulation in a QAM constellation are different. The ciphermodulation symbol representation is in a location non-coincident with an expected QAM constellation symbol. The symbol location of different plainmodulations when encypted using different modulation keys may be the same such that the corresponding ciphermodulation symbol representations are co-located. Different modulation keys are used for different plainmodulations, with a modulation key change occurring after transmission of a predetermined number of ciphermodulations and/or time. The modulation key and/or change is transmitted to enable coherent demodulation of the ciphermodulation to be performed. Multiple plainmodulations may be encrypted into a single ciphermodulation and/or a single plainmodulation may be encypted across multiple ciphermodulations.

In one possible implementation an in-situ property determination system includes a displacement tool configured for use in a wellbore. The displacement tool includes four or more pads symmetrically located about an axis of the displacement tool, with each pad having a contact surface configured to contact a wall of the wellbore. The four or more pads can extend from a first position proximate an outer surface of the displacement tool to a second position in contact with the wall of the wellbore such that the four or more pads deform the wellbore into an at least approximately circular cross section. The system also includes a recordation device to record force displacement information associated with extending the four or more pads from the first position to the second position.

Communication devices and a method of providing secure electronic content are general described. A plainmodulation containing user content is encrypted using a modulation key to form a ciphermodulation having a different magnitude and/or phase than the plainmodulation. Symbol representations of the plainmodulation and ciphermodulation in a QAM constellation are different. The ciphermodulation symbol representation is in a location non-coincident with an expected QAM constellation symbol. The symbol location of different plainmodulations when encypted using different modulation keys may be the same such that the corresponding ciphermodulation symbol representations are co-located. Different modulation keys are used for different plainmodulations, with a modulation key change occurring after transmission of a predetermined number of ciphermodulations and/or time. The modulation key and/or change is transmitted to enable coherent demodulation of the ciphermodulation to be performed. Multiple plainmodulations may be encrypted into a single ciphermodulation and/or a single plainmodulation may be encypted across multiple ciphermodulations.

A burst-mode phase shift keying (PSK) communications apparatus according to an embodiment of the present invention enables practical, power-efficient, multi-rate communications between an optical transmitter and receiver. Embodiments may operate on differential PSK (DPSK) signals. An embodiment of the apparatus includes an average power limited optical transmitter that transmits at a selectable data rate with data transmitted in bursts, the data rate being a function of a burst-on duty cycle. DPSK symbols are transmitted in bursts, and the data rate may be varied by changing the ratio of the burst-on time to the burst-off time. This approach offers a number of advantages over conventional DPSK implementations, including near-optimum photon efficiency over a wide range of data rates, simplified multi-rate transceiver implementation, and relaxed transmit laser line-width requirements at low data rates.

A symbol sending method, a symbol receiving method, a sending device, a receiving device, and a storage medium are disclosed. The method for symbol transmission may include determining, N+1 transmission symbols of s.sub.0, s.sub.1, s.sub.2, . . . s.sub.N, according to a reference symbol and (M+1)*N bits, where 0, 1, 2, . . . , N denote indices of the transmission symbols, s.sub.0 denotes the reference symbol; a transmission symbol indexed n is determined according to an amplitude and a phase of a transmission symbol indexed n1, and M+1 bits, and M is an integer greater than or equal to 1, N is an integer greater than or equal to 1, 1nN, n is an integer; and transmitting the N+1 transmission symbols.

A symbol transmitting method, including: determining N+1 transmission symbols s.sub.0, s.sub.1, s.sub.2, . . . , s.sub.N, according to a reference symbol and (M1+M2)*N bits, where 0, 1, 2, . . . , N are indices of the N+1 transmission symbols, s.sub.0 is a reference symbol, an amplitude of a transmission symbol with index n is determined according to M1 bits, a phase of the transmission symbol with index n is determined according to a phase of a transmission symbol with index n1 and M2 bits, M1 is an integer greater than or equal to 1. M2 is an integer greater than or equal to 1, N is an integer greater than or equal to 1, 1nN, and n is an integer; and transmitting the N+1 transmission symbols.