2 research outputs found
Cascading Sensor Network Clock Synchronization Scheme
In this paper, we propose a hybrid clock synchronization architecture for a
cascaded sensor network based on GPS time service and synchronous frame
protocol. The sensor's upper-level unit is called sensor management unit (SMU)
which synchronizes the local clock with the GPS and then use the broadcast sync
frame to synchronize the clock of the sensor chain. In this paper, we build a
link of 20 cascaded sensors to measure the center frequency and clock
stability. The results showed that the center frequency deviation was 0.037 Hz
and the stability was 0.045 ppm to 0.066 ppm .The stability of GPS is 0.06ppm,
the scheme has achieved the effect similar to installing GPS chip on every
sensor
Robust Clock Synchronization via Low Rank Approximation in Wireless Networks
Clock synchronization has become a key design objective in wireless networks
for its essential importance in many applications. However, as the wireless
link is prone to random network delays due to unreliable channel conditions, it
is in general difficult to achieve accurate clock synchronization among
wireless nodes. This letter proposes robust clock synchronization algorithms
based on low rank matrix approximation, which are able to correct timestamps in
the presence of random network delays. We design a low rank approximation based
maximum likelihood estimator (MLE) to jointly estimate the clock offset and
clock skew under the two-way message exchange mechanism assuming Gaussian delay
distribution. By formulating the timestamp correction problem into a low rank
approximation problem, we can solve the problem in the singular value
decomposition (SVD) domain and also via nuclear norm minimization. Numerical
results show that the proposed schemes can correct noisy timestamps and thus
achieve more robust synchronization performance than the MLE.Comment: 5 pages, 3 figure