CLIAMS:
1. A method comprising:
generating a preamble signal associated with a data packet, wherein the preamble signal comprises one or more blocks of synchronization sequence, and wherein each block of synchronization sequence comprises a plurality of basic sequences with an intermittent fractional shift of pre-determined time duration between consecutive basic sequences; and
transmitting the preamble signal to a receiver.

2. The method of claim 1, wherein each of the plurality of basic sequences is having preset length.

3. The method of claim 1, wherein each of the plurality of basic sequence comprises one or more periods.

4. The method of claim 1, wherein generating the preamble signal associated with the data packet comprises:
generating a basic binary sequence;
repeating the basic binary sequence for a pre-determined number of times;
converting the repetitive basic binary sequences into repetitive basic pulse sequences;
adding an intermittent fractional shift (aTs) between the consecutive basic pulse sequences to obtain a block of synchronization sequence;
repeating the block of synchronization sequence for a predetermined number of times; and
adding an intermittent fractional shift (ßTs) between the consecutive blocks of the synchronization sequence.

5. The method of claim 4, wherein the intermittent fractional shift (aTs) of pre-determined time duration is fractional multiple of time period of a single pulse.

6. The method of claim 4, wherein total sum of the intermittent fractional shifts (aTs) and the intermittent fractional shifts (ßTs) is equal to integral multiple of time period of a single pulse.

7. An apparatus comprising:
a preamble generating module configured for generating a preamble signal associated with a data packet, wherein the preamble signal comprises one or more blocks of synchronization sequence, and wherein each block of synchronization sequence comprises a plurality of basic sequences with an intermittent fractional shift of pre-determined time duration between consecutive basic sequences; and
a transmitting unit configured for transmitting the preamble signal to a receiver.

8. The apparatus of claim 7, wherein each of the plurality of basic sequences is having preset length.

9. The apparatus of claim 7, wherein each of the plurality of basic sequence comprises one or more periods.

10. The apparatus of claim 7, wherein in generating the preamble signal associated with the data packet, the preamble generation module is configured for:
generating a basic binary sequence;
repeating the basic binary sequence for a pre-determined number of times;
converting the repetitive basic binary sequences into repetitive basic pulse sequences;
adding an intermittent fractional shift (aTs) between the consecutive basic pulse sequences to obtain a block of synchronization sequence;
repeating the block of synchronization sequence for a predetermined number of times; and
adding an intermittent fractional shift (ßTs) between the consecutive blocks of the synchronization sequence.

11. A method of synchronizing an incoming baseband signal with sensitivity region of a receiver, comprising:
detecting presence of an incoming data packet based on a baseband signal corresponding to a preamble signal received from a transmitter;
setting start of the first symbol of the preamble signal corresponding to the detected data packet; and
synchronizing peak of each pulse of the preamble signal with sensitivity region of the receiver based on the start of the first symbol of the preamble signal.

12. The method of claim 11, wherein the preamble signal comprises one or more blocks of synchronization sequences, and wherein each block of synchronization sequence comprises a plurality of basic sequences with an intermittent fractional shift ((aTs)) of pre-determined time duration between the consecutive basic sequences.

13. The method of claim 12, wherein each of the basic sequences comprises one or more periods.

14. The method of claim 13, wherein detecting the presence of the incoming data packet based on the baseband signal corresponding to the preamble signal comprises:
computing a correlation value through correlating the baseband signal and a pre-determined basic sequence;
comparing the computed correlation value with a pre-determined threshold value; and
detecting the incoming data packet if the computed correlation value is greater than or equal to the pre-determined threshold value.

15. The method of claim 14, wherein computing the correlation value through correlating the baseband signal and the pre-determined basic sequence, comprises:
computing a correlation value for each of the periods in the basic sequence of the preamble signal; and
computing average correlation value through averaging the correlation values corresponding to the periods in the basic sequence.

16. The method of claim 15, wherein computing average correlation value through averaging the correlation values corresponding to the period in the basic sequence, comprises:
computing average correlation value through the averaging the averaged correlation values corresponding to the plurality of basic sequences of the block of synchronization sequence.

17. The method of claim 16, wherein setting the start of the first symbol of the preamble signal corresponding to the detected data packet comprises:
determining a presence of start frame delimiter (SFD) sequence in the incoming baseband signal by correlating the incoming baseband signal with a pre-determined SFD sequence;
determining whether correlation value obtained through correlating the incoming baseband signal with a pre-defined SFD sequence is greater than or equal to the pre-determined SFD sequence;
determining an index corresponding to the correlation value obtained through correlating the baseband signal and the pre-determined basic sequence if the correlation value obtained through correlating the incoming baseband signal with the pre-defined SFD sequence is less than the pre-determined SFD sequence;
computing a set of correlation values using the index value corresponding to the correlation value obtained through correlating the baseband signal and the pre-determined basic sequence;
identifying one or more correlation values which are greater than or equal to a pre-determined threshold;
estimating the start index of the preamble signal based on number of identified correlation values; and
setting the start of the first symbol of the preamble signal based on the estimated start index.

18. The method of claim 17, wherein synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the start index of the preamble signal comprises:
obtaining an average sample for each of the plurality of basic sequences in the preamble signal;
computing a pulse offset error metric using the obtained average samples;
estimating a shift required in a quench waveform with respect to the start index of the preamble signal to synchronize the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the computed pulse offset error metric; and
synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the estimated shift in the quench waveform.

19. The method of claim 18, wherein estimating the shift required in the quench waveform using the pulse offset error metric comprises:
determining the shift required in the quench waveform corresponding to the pulse offset error metric using a look up table.

20. The method of claim 17, wherein synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the start index of the preamble signal comprises:
identifying an index corresponding to a maximum correlation value from the identified correlation values;
estimating a shift required in the quench waveform with respect to the start index of the preamble signal to synchronize the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the identified index value; and
synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the estimated shift in the quench waveform.

21. An apparatus comprising:
a packet detection module configured for detecting presence of an incoming data packet based on a baseband signal corresponding to a preamble signal received from a transmitter;
a symbol synchronization module configured for setting start of the first symbol of the preamble signal corresponding to the detected data packet; and
a pulse synchronization module configured for synchronizing peak of each pulse of the preamble signal with sensitivity region of the receiver based on the start of the first symbol of the preamble signal.

22. The apparatus of claim 21, wherein the preamble signal comprises one or more blocks of synchronization sequences, and wherein each block of synchronization sequence comprises a plurality of basic sequences with an intermittent fractional shift ((aTs)) of pre-determined time duration between the consecutive basic sequences.

23. The apparatus of claim 22, wherein each of the basic sequences comprises one or more periods.

24. The apparatus of claim 23, wherein in detecting the presence of the incoming data packet based on the baseband signal corresponding to the preamble signal, the packet detection module is configured for:
computing a correlation value through correlating the baseband signal and a pre-determined basic sequence;
comparing the computed correlation value with a pre-determined threshold value; and
detecting the incoming data packet if the computed correlation value is greater than or equal to the pre-determined threshold value.

25. The apparatus of claim 24, wherein in computing the correlation value through correlating the baseband signal and the pre-determined basic sequence, the packet detection module is configured for:
computing a correlation value for each of the periods in the basic sequence of the preamble signal; and
computing average correlation value through averaging the correlation values corresponding to the periods in the basic sequence.

26. The apparatus of claim 25, wherein in computing the average correlation value through averaging the correlation values corresponding to the period in the basic sequence, the packet detection module is configured for:
computing average correlation value through the averaging the averaged correlation values corresponding to the plurality of basic sequences of the block of synchronization sequence.

27. The apparatus of claim 26, wherein in setting the start of the first symbol of the preamble signal corresponding to the detected data packet, the symbol synchronization module is configured for:
determining a presence of start frame delimiter (SFD) sequence in the incoming baseband signal by correlating the incoming baseband signal with a pre-determined SFD sequence;
determining whether correlation value obtained through correlating the incoming baseband signal with a pre-defined SFD sequence is greater than or equal to the pre-determined SFD sequence;
determining an index corresponding to the correlation value obtained through correlating the baseband signal and the pre-determined basic sequence if the correlation value obtained through correlating the incoming baseband signal with the pre-defined SFD sequence is less than the pre-determined SFD sequence;
computing a set of correlation values using the index value corresponding to the correlation value obtained through correlating the baseband signal and the pre-determined basic sequence;
identifying one or more correlation values which are greater than or equal to a pre-determined threshold;
estimating the start index of the preamble signal based on number of identified correlation values; and
setting the start of the first symbol of the preamble signal based on the estimated start index.

28. The apparatus of claim 27, wherein in synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the start index of the preamble signal, the pulse synchronization module is configured for:
obtaining an average sample for each of the plurality of basic sequences in the preamble signal;
computing a pulse offset error metric using the obtained average samples;
estimating a shift required in a quench waveform with respect to the start index of the preamble signal to synchronize the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the computed pulse offset error metric; and
synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the estimated shift in the quench waveform.

29. The apparatus of claim 28, wherein in estimating the shift required in the quench waveform using the pulse offset error metric, the pulse synchronization module is configured for:
determining the shift required in the quench waveform corresponding to the pulse offset error metric using a look up table.

30. The apparatus of claim 27, wherein in synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the start index of the preamble signal, the pulse synchronization module is configured for:
identifying an index corresponding to a maximum correlation value from the identified correlation values;
estimating a shift required in the quench waveform with respect to the start index of the preamble signal to synchronize the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the identified index value; and
synchronizing the peak of each pulse of the preamble signal with the sensitivity region of the receiver based on the estimated shift in the quench waveform.
31. A system comprising:
a transmitter configured for generating a preamble signal associated with a data packet; and transmitting the preamble signal, wherein the preamble signal comprises one or more blocks of synchronization sequence, and wherein each block of synchronization sequence comprises a plurality of basic sequences with an intermittent fractional shift of pre-determined time duration between consecutive basic sequences; and
a receiver configured for:
detecting presence of an incoming data packet based on a baseband signal corresponding to a preamble signal received from a transmitter;
setting start of the first symbol of the preamble signal corresponding to the detected data packet; and
synchronizing peak of each pulse of the preamble signal with sensitivity region of the receiver based on the start of the first symbol of the preamble signal.
,TagSPECI:FIELD OF THE INVENTION

The present invention relates to field of communication systems, and more particularly relates to timing synchronization in a wireless communication system.

BACKGROUND OF THE INVENTION

Receivers such as super regenerative receiver (SRR) are Ultra low-power Radio receivers for low-data rate applications. A basic structure of SRR includes an antenna, low noise amplifier (LNA), super regenerative oscillator (SRO), envelope detector (ED), automatic gain control (AGC), quench waveform generator and baseband filter (BBF). The principle of working of SRR is based on a repeated build-up and decay of self-generated oscillations in the super regenerative oscillator having frequency near to Radio Frequency (RF) signal frequency intercepted by the antenna. Super regenerative receivers are typically used in low power Body Area Networks, remote control systems such as garage door openers, robots, model ships, airplanes etc., short distance telemetry and wireless security.

Generally, frequency selectivity of the SRR is directly affected by over quenching rate (OQR) of a quench signal. Currently, each data symbol is oversampled by a quench signal operating at a quench rate considerably higher than data rate. This translates into relatively low frequency selectivity and an equivalent noise bandwidth that is much larger than the signal bandwidth. Thus, the SRR is susceptible to out-of-band interference. Hence, it is desirable to maintain the OQR as low as possible. However, a higher OQR is needed to ensure that a plurality of outputs is obtained for each incoming pulse envelope in the SRR. From these outputs, a fractional sampling rate is chosen so as to maximize overall energy capture of incoming signal. Thus, it is clear that in order to improve interference rejection, a lower OQR is desirable. On the contrary, improved synchronization performance necessitates a higher OQR.

BRIEF DESCRIPTION OF THE ACCCOMPANYING DRAWINGS

Figure 1 illustrates a block diagram of an exemplary wireless communication system, according to one embodiment.

Figure 2 illustrates an exploded view of a transmitter such as those shown in Figure 1, according to one embodiment.

Figure 3 is a process flowchart illustrating an exemplary method of generating a preamble signal, according to one embodiment.

Figure 4 is a diagrammatic representation illustrating an exemplary basic binary sequence used for generating the preamble signal.

Figure 5 illustrates an exploded view of a receiver such as those shown in Figure 1, according to one embodiment.

Figure 6 is a process flowchart illustrating an exemplary method of a timing synchronization at the receiver, according to one embodiment.

Figure 7 is a process flowchart illustrating an exemplary method of detecting incoming data packet based on a baseband signal, according to one embodiment.

Figure 8 is a process flowchart illustrating an exemplary method of setting start of a preamble signal corresponding to a detected data packet, according to one embodiment.

Figure 9 is a process flowchart illustrating an exemplary method of synchronizing peak of each pulse of the preamble signal corresponding to the detected data packet with the sensitivity region of the receiver, according to one embodiment.

Figures 10A and 10B are schematic representations depicting synchronization of peak of each of the preamble signal with the sensitivity region of the SRR.

Figure 11 illustrates a block diagram of a Super Regenerative Receiver (SRR), according to one embodiment.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION OF THE INVENTION

Timing synchronization in a wireless communication system is disclosed. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

Figure 1 illustrates a block diagram of an exemplary wireless communication system 100, according to one embodiment. In Figure 1, the wireless communication system 100 includes a receiver 102, a transmitter 104, and a wireless network 106. The transmitter 104 and receiver 102 are wirelessly connected through the wireless network 106. The receiver 102 may be a super regenerative receiver (SRR).

Typically, in the wireless communication system 100, the transmitter 104 generates and transmits data packet including a preamble signal, a start frame delimiter, and data payload. The preamble signal includes a plurality of blocks of synchronization sequence (also referred to as training sequences) with a first intermittent fractional shift between the consecutive blocks of synchronization sequences. Each block of synchronization sequence includes repetitive basic sequences with a second intermittent fractional shift between the basic sequences. Further, each basic sequence contains one or more periods (P) with good correlation properties.

The receiver 102 continuously determines presence of data packet in air. When the transmitter 104 transmits the preamble signal in the form of baseband signal, the receiver 102 detects presence of the data packet in the air based on the incoming baseband signal. Once the data packet is detected, the receiver 102 determines start of the preamble signal and synchronizes peak of each pulse of the preamble signal with sensitivity region of the receiver 102 by shifting a quench waveform having an over quenching rate equal to 1 with respect to the start of the preamble. A sensitivity region of the receiver 102 corresponds to the region where the regenerative gain of the SRR has a significant value. For example, the sensitivity region of SRR may be the negative slop zero crossing of the quench waveform or any other arbitrary point where the regenerative gain of SRR is significant. Accordingly, the quench waveform is shifted such that the combination of the incoming baseband signal and the sensitivity region maximizes the regenerative gain of the SRR. Thereafter, the receiver 102 processes the remaining incoming baseband signal and proceeds with data detection.

Figure 2 illustrates an exploded view of the transmitter 104, according to one embodiment. The transmitter 104 includes a data packet generation module 202, and a transmitting unit 204. The data packet generation module 202 includes a preamble generation module 206. The data packet generation module 202 is configured for generating data packets carrying data intended for the receiver 102. Each of the data packets includes a preamble signal, a start frame delimiter (SFD), and payload data. According to the present invention, the preamble generation module 206 is configured for generating a preamble signal. The preamble signal enables the receiver 102 to perform timing synchronization with the transmitter 104. For generating a preamble signal, the preamble generation module 206 selects a basic binary sequence with good correlation properties. The basic binary sequence may be inherently periodic with P periods and length L. For example, the basic binary sequence may be a pseudo noise (PN) sequence (formed using 0s and 1s) with length L and P Periods, as shown in Figure 4. The preamble generation module 206 repeats the basic binary sequence for a pre-defined number of times (e.g., Q = 3). The preamble generation module 206 converts the basic binary sequences into basic pulse sequences using a pulse shaping filter. In one exemplary implementation, the basic binary sequences are upsampled by a specific factor and then 1s in the upsampled basic binary sequences are translated into discrete waveforms of a prescribed pulse shape with an associated time period (Ts) using a Gaussian filter or a raised cosine filter. Consequently, basic pulse sequences containing pulses and zeros of length LPTs with Q repetition is obtained.

Thereafter, the preamble generation module 206 introduces intermittent fractional shift of duration equal to aTs between the basic pulse sequences, where Ts is a time period of a single pulse and value of a lies between 0 to 1. The value of ‘a’ is selected such that different portions of pulses in the basic pulse sequences fall within the sensitivity region of the receiver 102 during each of the basic pulse sequences. Typically, the value of a is equal to Ts/4. It can be noted that, the intermittent fractional shift (aTs) is a fractional multiple of time period of a single pulse. For example, for repetition of binary pulse sequences (Q) = 3, the preamble generation module 206 introduces the intermittent fractional shift between the first basic pulse sequence and the second basic pulse sequence, another intermittent fractional shift between the second basic pulse sequence and the third basic pulse sequence. Hence, when Q=3, the preamble generation module 206 introduces Q-1 intermittent fractional shifts. The intermittent fractional shift is introduced as sensitivity region of the receiver 102 occurs at different positions of pulses in different portions of the preamble signal and energy capture of the receiver 102 changes for each period of the preamble signal. In this manner, the preamble generation module 206 generates a single block of synchronization sequence containing repetitive basic pulse sequences of length LPTs with intermittent fractional shift of aTs between the two basic pulse sequences. In some embodiments, the preamble generation module 206 may generate a plurality of blocks of synchronization sequences with intermittent fractional shifts (ßTs) between the blocks of synchronization sequences such that sum of total of the fractional shifts (Q-1)aTs + ßTs (i), where i =1-(Z-1) is an integral multiple of the time period of one pulse (Ts). This ensures that each of the blocks of synchronization sequence behave in the same manner at the receiver 102 as each of corresponding portions of block of synchronization sequence influences the sensitivity region of the receiver 102. The value of ß is selected such that each block of synchronization sequences behaves in a similar fashion when passed through the receiver 102. Typically, ß = Ts/2 when Q = 3 and a = Ts/4. However, the value of ß may range from 0 to 1.

As described above, the block(s) of synchronization sequence is followed by a SFD sequence (s(t)). A SFD sequence is added to obtain a good estimate of start of a first symbol of the preamble signal. For example, a SFD sequence is a binary sequence [e.g., 01011001] of length 8 or 16 with good correlation properties which is upsampled and passed through a pulse shaping filter.

Once the data packet is generated, the transmitting unit 204 transmits the data packet with the preamble signal to the receiver 102.

Figure 3 is a process flowchart 300 illustrating an exemplary method of generating a preamble signal, according to one embodiment. At step 302, a basic binary sequence with number of periods (P) and length L having good correlation properties is generated. For example, the basic binary sequence may be a pseudo noise (PN) sequence. At step 304, the basic binary sequence is repeated for pre-determined number of times (Q). At step 306, the repetitive basic binary sequence is converted into repetitive basic pulse sequence with zeros and pulses using a pulse shaping filter.

At step 308, an intermittent fractional shift (aTs) is added between the basic pulse sequences to form a block of synchronization sequence. At step 310, the block of synchronization sequence is repeated for a predetermined number of times. At step 312, an intermittent shift (ßTs) is added between the blocks of synchronization sequence to obtain a preamble signal. It can be noted that the steps 310 and 312 are optional. In other words, the preamble signal may contain a single block of synchronization sequence instead of plurality of blocks of synchronization sequence.

Figure 5 illustrates an exploded view of the receiver 102, according to one embodiment.
The receiver 102 includes an ADC 501, a timing synchronization module 500, a quench waveform generator 506, and a data detection module 510. The timing synchronization module 500 includes a packet detection module 502, symbol synchronization module 504 and a pulse synchronization module 508.

The analog to digital converter (ADC) 501 converts an incoming baseband signal in analog form to a digital form. The packet detection module 502 continuously monitors presence of data packet in the air based on input signal received from the ADC 501. When the transmitter 104 transmits the data packet in the form of baseband signal, the receiver 102 determines presence of the data packet based on the incoming baseband signal. Upon detecting the data packet, the symbol synchronization module 504 estimates start index of the preamble signal corresponding to the detected data packet and sets start of the first symbol of the preamble signal based on the estimated start index. The pulse synchronization module 508 calculates shift (?) required in a quench waveform in order to synchronize peak of each pulse of the preamble signal corresponding to the detected data packet with the sensitivity region of the SRR. In some embodiments, the quench waveform generated has an over quenching rate (OQR) equal to 1. Further, the pulse synchronization module 506 provides the information required for synchronizing peak of each pulse of the remaining incoming baseband signal with the quench waveform. The data detection module 510 processes the remaining incoming baseband signal after synchronization of peak of the pulse of the remaining baseband signal and detects payload data in the data packet.

Figure 6 is a process flowchart 600 illustrating an exemplary method of a timing synchronization at the receiver 102, according to one embodiment. When the transmitter 104 transmits a baseband signal corresponding to the preamble signal to the receiver 102, the receiver 102 synchronizes its timing with the transmitter 104 as given in steps 602 to 606.

At step 602, an incoming data packet is detected based on a baseband signal received from the transmitter 104. The baseband signal corresponds to a data packet carrying a preamble signal transmitted by the transmitter 104. The preamble signal includes one or more blocks of synchronization sequence, each block of synchronization sequence includes basic pulse sequences with an intermittent fractional shift of pre-determined time duration (aTs) between the consecutive basic sequences. The basic sequences with the shift of pre-determined time duration enable the receiver to detect an incoming data packet. The detailed process of detecting an incoming data packet is illustrated in Figure 7.

At step 604, start index of the preamble signal corresponding to the detected data packet is estimated and start of the first symbol of the preamble signal is set based on the estimated start index. When the data packet is detected, an index at which the data packet is detected is determined. Further, a number of peaks existing around the index of the detected data packet are determined. Based on the number of peaks, an index corresponding to the farthest peak around the index of the detected data packet is determined as the start index of the preamble signal. Based on the start index, the start of the first symbol of the preamble signal is set. The detailed process of determining the start index of the preamble signal is illustrated in Figure 8.

At step 606, peak of each pulse of the preamble signal corresponding to the detected data packet is synchronized with sensitivity region of the receiver 102 based on the start of the first symbol of the preamble signal. In some embodiments, the peak of each pulse is synchronized with the sensitivity region of the receiver 102 by shifting the quench waveform from the start of the first symbol of the preamble signal till the peak of each pulse falls within the sensitivity region of the receiver 102. The detailed process of synchronization of the sensitivity region with the peak of said each pulse is illustrated in Figure 9.

Figure 7 is a process flowchart 700 illustrating an exemplary method of detecting incoming data packet based on a baseband signal, according to one embodiment. At step 702, an incoming baseband signal is received. The baseband signal may correspond to a preamble signal transmitted by the transmitter 104. The preamble signal contains one or more training sequences; each training sequence contains one or more basic sequences. Each basic sequence contains one or more periods (P). At step 704, a normalized sliding correlation value is computed through correlating the incoming baseband signal (y(t)) with a predefined basic sequence (x(t)). In some embodiments, a single period of the basic sequence (x(t)) is correlated with the incoming baseband signal (y(t)) to obtain correlation value. In these embodiments, the correlation value for single period of the basic sequence is computed using the following equation:

… Eq. 1
where, L is length of the basic sequence of P periods .
Further, and …Eq. 1a
…Eq. 1b
In one embodiment, in order to minimize the probability of false alarm, the incoming data packet is detected based on a baseband signal when the incoming signal , .

If the preamble signal contains a basic sequence with a single period (i.e., P=1), a single correlation value is obtained. However, when the preamble signal contains a basic sequence with more than one period, then the correlation value for each of the periods (P) in the basic sequence is computed using the equation (Eq.1). Further, the correlation values are averaged to obtain an averaged correlation value using the following equation:

….Eq. 2

Further, if the preamble signal contains multiple blocks of synchronization sequences, then the average correlation values for the blocks of synchronization sequence is averaged using the following equation:

…Eq. 3
…Eq. 3a
where, Z is the number of basic sequences in the preamble signal.

At step 706, the correlation value (Rxy) is compared with a pre-determined threshold value. (Tp). The predetermined threshold is computed based on requisite probability of missed detection and probability of false alarm. The threshold value Tp is chosen such that the threshold value Tp meets probability of missed detection under a constraint on the probability of false alarm. For example, the threshold is set to around 0.6 to 0.8.

At step 708, it is determined whether the correlation value (Rxy) is greater than the pre-determined threshold value (TP). If the correlation value (Rxy) is greater than the pre-determined threshold value (TP), then at step 710, a data packet is declared as detected.

Figure 8 is a process flowchart 800 illustrating an exemplary method of setting start of the preamble signal corresponding to the detected data packet, according to one embodiment. At step 802, a presence of a start frame delimiter (SFD) sequence in the incoming baseband signal (y(t)) is detected by correlating the incoming baseband signal (y(t)) with a pre-defined SFD sequence (s(t)). In some embodiments, the incoming baseband signal (y(t)) is correlated with the pre-defined SFD sequence (s(t)) using the following equation:

... Eq. 4
Wherein Ls is the length of the pre-defined SFD sequence (s(i)).

At step 804, it is determined whether the correlation value (Rsy) obtained from the Eq. (5) is greater than or equal to a pre-determined threshold value (Tf). The threshold value Tf is chosen such that the threshold value Tf meets probability of missed detection under a constraint on probability of false alarm. For example, the threshold is set to around 0.7 to 0.8. If the correlation value (Rsy) is greater than or equal to the pre-determined threshold value (Tf), then it implies that the SFD sequence (s(t)) is present in the incoming baseband signal (y(t)). If the correlation value (Rsy) is less than the pre-determined threshold value (Tf), then it implies that the SFD sequence (s(t)) is not present in the incoming baseband signal (y(t)).

If the SFD sequence (s(t)) is detected, then at step 806, a symbol synchronization point is determined. In some embodiments, the symbol synchronization point may correspond to point where the SFD sequence (s(t)) is detected in the incoming baseband signal (y(t)). If the SFD sequence (s(t)) is not detected, then at step 808, index value (tp) corresponding to the correlation value (Rxy) is determined. The correlation value (Rxy) is value at which the incoming data packet is detected.

At step 810, a set of correlation values ?xy are computed using the determined index value (tp). The correlation values ?xy are computed using the following equation:

… Eq.5

For example, if the number of basic sequence (Q) is 3, then set of correlation values may be represented as following set:

…Eq.5a
The above set of correlation values may be generalized using following equation:

…Eq. 5b

At step 812, one or more correlation values which are equal to or greater than a pre-determined threshold (Ts) are identified from the set of correlation values. The threshold value Ts is chosen such that the threshold value Ts meets probability of missed detection under a constraint on probability of false alarm. For example, the threshold is set to around 0.4 to 0.8. At step 814, a start index (ts) of the preamble signal is estimated based on the number of correlation values identified at step 812. The start index (ts) indicates start of the first symbol of the preamble signal transmitted by the transmitter 104. At step 816, start of the first symbol of the preamble signal is set based on the start index (ts) of the preamble signal.

For example, if the number of correlation values is greater than or equal to number of basic sequences (Q) in the preamble signal, minimum value of an index (ts) corresponding to one of the identified correlation values is set as start of the first symbol of the preamble signal.

Alternatively, difference of index values between the first correlation value and the second correlation value, and difference of index between the second correlation value and the third correlation value are computed. If the difference of the index values is equal to Q and Q+1 respectively, then correlation value is computed by correlating the incoming baseband signal (y(t) with the pre-defined SFD sequence (s(t)) at shifts of around Q from the maximum index (tPmax) of the one or more correlation values identified in step 812. For example, the correlation value is computed using the following equation:

…Eq. 6

Further, a maximum correlation value (Rsy) is selected from the correlation values obtained using the Eq. 7 and compared with the pre-determined threshold value (Tf). If the maximum correlation value exceeds the pre-determined threshold value, then start of the first symbol is offset by an offset duration from the index corresponding to the maximum correlation value. The offset duration is computed using the following equation:

…Eq. 7
where is an index value corresponding to the correlation value using which the SFD sequence (s(t)) is detected in the incoming baseband signal (y(t)).

The above process of estimating the start of the first symbol is generally applicable in case where low amplitude portion of the first period in the basic sequence of the preamble signal fall within sensitivity region of the receiver 102.

If the duration between successive correlation values is greater than Q+1, an index (ts) corresponding to minimum of the successive correlation values is determined as start of the first symbol of the preamble signal (ts). On the other hand, if the number of correlation values is less than number of the basic sequences (Q) of the preamble signal, correlation value is computed by correlating the incoming baseband signal (y(t)) with the pre-defined SFD sequence (s(t)) at shifts of (L * P) from the maximum index (tPmax) of the correlation values identified in step 812. For example, the correlation value (Rsy (tpmax + LP)) is computed using the following equation:

…Eq. 8

Further, a maximum correlation value (Rsy (tpmax + LP)) is compared with the pre-determined threshold value (Tf). If the maximum correlation value (Rsy (tpmax + LP)) exceeds the pre-determined threshold value (Tf), then the start of the first symbol (ts) is computed using the following equation:

…Eq. 9

If the maximum correlation value (Rsy (tpmax + LP)) is less than the pre-determined threshold value (Tf), then the index (ts) of the minimum of the correlation values is selected as start of the first symbol of the preamble signal. If the number of identified correlation value (Rsy (tpmax + LP)) is equal to one, then the index (ts) corresponding to the identified correlation value (Rsy (tpmax + LP)) is considered as a start of the first symbol of the preamble signal.

Once the start of the preamble signal is set at the start index (ts), the incoming baseband signal with the set start of the preamble signal (ys(t)) is provided to the pulse synchronization module 510 for synchronizing peak of each pulse of the preamble signal with the sensitivity region of the receiver 102 as described in the following description.

Figure 9 is a process flowchart 900 illustrating an exemplary method of synchronizing peak of each pulse of the preamble signal corresponding to the detected data packet with the sensitivity region of the receiver 102, according to one embodiment. At step 902, status of the pulse synchronization flag is determined. During estimation of the start index of the preamble signal, the pulse synchronization flag is set to ‘0’ or ‘1’. The pulse synchronization flag indicates that synchronization of the peak of each pulse with the sensitivity region of the receiver 102 needs to be performed when the pulse synchronization flag is set to ‘0’. On the other hand, when the pulse synchronization flag is set to ‘1’, synchronization of peak of each pulse is not to be performed. For example, the pulse synchronization flag is set to ‘1’ when low amplitude portions of the first period fall within the sensitivity region of the receiver 102. Also, the pulse synchronization flag is set to ‘1’ when number of correlation values are less than Q-1 and maximum of the correlation values is greater than the predetermined threshold value (Tf).

At step 904, it is determined whether the pulse synchronization flag is set to ‘1’. If the pulse synchronization flag is set to ‘1’, then at step 906, quench waveform of the receiver 102 is shifted by duration equal to Ts/2 and the incoming data packet is processed based on the shifted quench waveform.

If the pulse synchronization flag is set to ‘0’, then at step 908, an average sample corresponding to each period of the basic sequence in the preamble signal is obtained. For example, if the basic sequence has three periods (i.e., P=3), then average sample
S? corresponding to the three periods is computed using the following equations:

… Eq. 10
… Eq. 11
… Eq. 12

Alternatively, the average samples S? (1), S? (2), and S? (3) are computed for 1s in the basic sequences of the preamble signal using the above equations 11, 12 and 13.

At step 910, a pulse offset error metric ß? is computed using the obtained average samples. For example, the pulse offset error metric ß? is computed using the following equation:

…Eq. 13

At step 912, a shift (?) required in the quench waveform with respect to the start of the first symbol of the preamble signal is estimated using the pulse offset error metric ß?. In some embodiments, the shift (?) required in the quench waveform corresponding to the pulse offset error metric ß? is estimated using in a lookup table. The look up table contains N values of pulse offset error metric ß? and corresponding shift (?) required in the quench waveform as the pulse offset error varies from 0 to T. At step 914, peak of each pulse of the preamble signal is synchronized with sensitivity region of the receiver 102 by shifting the quench waveform from the start of the first symbol of the preamble signal by the determined shift value (?). Consequently, the sensitivity region of the quench waveform is aligned with the peak of each pulse of the incoming baseband signal in order to maximize the regenerative gain. This is possible due to the addition of the intermittent fractional shifts (aTs and/or ßTs) in the preamble signal since different portions of the incoming baseband signal fall within the sensitivity region of the receiver 102 during different portions of the preamble signal. Once the peak of each pulse is synchronized, the quench waveform and the incoming baseband signal are fed again for further processing.

The value of ? computed at step 912 may be applicable in the case where number of basic sequences in a block of synchronization sequence (Q) is less than or equal to 3. However, when Q > 3, fractional shift ? or Tfoff required in the quench waveform with respect to the start of the first symbol of the preamble signal is estimated using the following equation:
?=[N_max/LP]aT_s …Eq.14

where, Nmax is index corresponding maximum correlation value obtained from a set of correlation values greater than a pre-determined threshold (Ts) are identified at step 812 of Figure 8

Figures 10A and 10B are schematic representations depicting synchronization of peak of each of the preamble signal with sensitive region of the quench waveform. In Figure 10A, the schematic representation 1000 illustrates correlation between an incoming baseband signal 1002 corresponding to a preamble signal and a quench waveform 1004 having an over quenching rate (OQR) of 1. It can be seen that, the incoming baseband signal 1002 is having an interment fractional shift 1006 between basic sequences of the preamble signal. Also, it can be seen that, the quench waveform 1004 has a sensitivity region 1008 away from peak of each pulse of the incoming baseband signal.
Referring to Figure 10B, the schematic representation 1050 illustrates shifting of the quench waveform to synchronize peak of each pulse of the preamble signal by a shift duration 1052 from start index 1054. It can be seen that, by shifting the quench waveform by the shift duration 1052, peak of each pulse of the preamble signal synchronized with the sensitivity region of the receiver 102 as indicated by reference numeral 1056.

Figure 11 illustrates a block diagram of an exemplary Super Regenerative Receiver (SRR) 1100, according to one embodiment. The SRR 1100 is an exemplary embodiment of the receiver 102 of Figure 1. The SRR 1100 includes an antenna 1102, a low noise amplifier (LNA) 1104, a super regenerative oscillator (SRO) 1108, an envelope detector 1108, low pass filter 1110, the ADC 501, the timing synchronization module 500, the quench waveform generator 506 and the data detection module 510.

As shown in Figure 11, the timing synchronization module 500 connected to the ADC 501 detects a data packet in air corresponding to a preamble signal, determines start index of the preamble signal, and computes a shift in a quench waveform to synchronize peak of pulse of an incoming baseband signal corresponding to the preamble signal with the sensitivity region of the SRR. The start index and the shift required in the quench waveform is provided to the quench waveform generator 504 so that the SRO 1106 synchronizes peak of each pulse of the remaining incoming baseband signal with the sensitive region of the quench waveform. The components of the SRR 1100 such as the antenna 1102, the LNA 1104, the SRO 1106, the envelope detector 1108, and the LPF 1110 are well known to the person skilled in the art and hence the explanation is thereof omitted.

The present embodiments have been described with reference to specific example embodiments; it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.