Decoding. The next task is decoding binary sequence from the encoded chirp. For the frequency domain energy distribution of a received overlapped signal, the fluctuations over frequencies is caused by both the message encoding on coding frequencies and the channel frequency selectivity. It is difficult to separate the information of encoding information (called message re- sponse) from the impact of channel selectivity (called channel ACR). Meanwhile, the channel ACR also introduces noise for message decoding. To address this problem, we find that acoustic channel frequency selectivity is stable with the same devices and the same multipath environment as shown in section II-B. The impact of channel selectivity on the pure chirp and the overlapped signal is the same. We can use the ACR from the pure chirp as the channel ACR of the overlapped signal. As we have obtained the channel ACR features of pure chirp in bidirectional initial authentication, message response of the overlapped signal can be obtained by subtracting the channel ACR. The frequency domain energy distribution of a received pure chirp A1 and a received overlapped signal A2 are shown in figure 9(a). We can derive message response in figure 9(b) by A2 A1. In the message response, the presence of spikes on coding frequencies indicates ‘1’ and ‘0’ otherwise. Meanwhile, we can see that the impact of channel frequency selectivity is very small in the message response as shown in Figure 9(b). In order to remove the base energy difference over frequencies, we normalize the message response by subtracting the slip average of message response as shown in figure 9(b). The normalized message response is shown in Figure 9(c). We can easily distinguish the bits ‘1’ from ‘0’ by their energy levels. To reduce the decoding bit error rate, we further calculate the first derivative of the curve in Figure 9(c). The result is shown in Figure 9(d). Then we decode ‘1’ and ‘0’ based on the resulted energy distribution.
Decoding. We use the Xxxxx (Xxxxx et al., 2007) decoder, a bottom-up synchronous parser that implements the CYK+ algorithm (Xxxxxxxxxx and Xxxxxx, 1998) with cube pruning (Xxxxxx, 2007). The constraint model requires some changes to decoding, which we briefly describe here:
Decoding. Decoding of bit streams will be done using one or other standardised decoders from the MPEG family. MPEG 4 AAC and MPEG-H are the two main ones that will be used for object-based audio. Legacy, channel-based, systems (such DAB, DVB) will use MPEG 1 Layer II or AAC. The behaviour of these decoders is well specified in the respective standards.
Decoding. Bob, Eve 1, and Xxx 2 receive the output systems Bn, En, and En in the state 1 2 m0,A1,A2 BnEnEn O= ρ x0,i(m0),x1,i(m0,A1),x2,i(m0,A1,A2) BE1E2
Decoding. The legitimate decoder, upon observing the chan- nel output yn, estimates un(mˆ u) such that (yn, tn, un(mˆ u)) ∈ T (n)(Y, T, U ) (37) where (a) deduces from the security condition, (b) follows from the Fano’s inequality, (c) can be derived from the Markov chain K0 (Xn, Xn) (Y n, Zn). (d) can be obtained by considering .
Decoding. The BMP decoder converts CDR files from one Ericsson or Nokia format (agreed from WP2) to the BMP internal format. Processing The BMP processing scripts (written in TCL/JAVA languages) will perform: o Perform all checks that FIH used to perform (while converting input CDR files to UTX format). o Load the THUFITAB table with a new row for each new CDR file. This task was previously performed by the DIH BSCS processes. o Duplicate record check both on CDR level and file level. Replaces the DRH BSCS batch process o Consolidation of "long duration calls". Replaces the AIH BSCS batch process. Encoding The BMP encoder produces output CDR files in BSCS UTX format. Disk Distribution UTX output files will be saved to a location which will point directly to the $WORK_DIR/MP/SWITCH directory on the BSCS server. This directory will be NFS mounted on the BSCS server. In this way it will be easy to keep track of all CDR files and it simplifies the backup procedure.
Decoding. Files that BMP has collected from network elements or other external systems and which require processing are converted to BMP's internal ASN.1 format.
