Dr. Tripathi, a Principal Consultant at Award Solutions, joined Award Solutions in March 2004, bringing his knowledge and experience in mobile wireless technologies to facilitate the planning, development and delivery of technical training seminars. He teaches and consults on various technologies including, LTE E-UTRAN and EPC, WiMAX, UMTS R99, HSDPA, HSUPA, HSPA+, 1xEV-DO, IMS, and WiMAX. He has taught various aspects of 3G and 4G commercial cellular technologies including but not limited to network operations, network planning, and network optimization.
Since receiving his doctorate in Wireless Communications from Virginia Tech, Dr. Tripathi has held several strategic positions in the wireless arena. For Nortel Networks, he worked to analyze and optimize the performance of CDMA networks, in such areas as load balancing, handoff, power control, supplemental channel management, and switch antenna diversity. As a Senior Systems Engineer and Product Manager for Huawei Technologies, Dr. Tripathi worked on the infrastructure design and optimization of CDMA2000, 1xEV-DO, and UMTS radio networks. He has significant experience designing, analyzing, and field-testing Radio Resource Management algorithms for CDMA2000 and 1xEV-DO.
In 2001, he co-authored a book on Radio Resource Management, and he is the author of numerous research papers and patent submissions. He has contributed chapters to two books on applications of fuzzy logic to communications and applicability of network neutrality principles to wireless systems. He is a co-author of an upcoming book on cellular communications (to be published by IEEE/Wiley).
Dr. Tripathi's position at Award Solutions puts him at the forefront of emerging technologies. He has authored courseware related to LTE, WiMAX, 1xEV-DO, HSUPA, UMTS optimization, 1xEV-DO RF optimization, advanced antenna techniques, and IP convergence. In addition to teaching the students in the Industry, he also trains his colleagues (i.e., instructors) on various technologies (e.g., LTE, WiMAX, 1xEV-DO, HSDPA, HSUPA, 802.11n, and advanced antenna techniques). His extensive knowledge, hands-on experience with commercial deployments, and enthusiasm for the subject matter, coupled with a passion for teaching, provide the foundation for consistently enjoyable, informative, and effective classes.
There has been a lot of action in Release 8 and Release 10
of UMTS (Universal Mobile Telecommunication System). Release 8 introduces LTE (Long Term
Evolution), while Release 10 defines LTE-Advanced. Release 9 does not get much limelight amidst
the comprehensive volume of work done in these two releases. However, Release 9 does have its place in
history- among other things, it provides a framework for finding the UE
location (so-called UE positioning) to support a variety of location services
(LCS) (e.g., emergency calls and directions to a restaurant). Release 9 specifies a variety of UE
positioning techniques essential to the offering of the LCS. We will focus on Positioning Reference
Signals (PRS) that can be used to facilitate determination of the position or
location of the UE by a UE-assisted positioning technique. A UE-assisted positioning technique implies
the following: (i) the UE makes some radio signal measurements, and (ii) the
network determines the UE location (e.g., latitude and longitude) by processing
the measurements reported by the UE.
Let's briefly discuss the PRS now. The PRS are transmitted on antenna port 6 and
do not use the resource elements allocated to Physical Broadcast Channel, Primary
Synchronization Signal, and Secondary Synchronization Signal. The PRS are sent in a configurable number of
consecutive subframes, which could be just one subframe or as many as 5
subframes. The E-UTRAN configures the
PRS bandwidth (e.g., a certain number of resource blocks) and the periodicity
of the PRS (e.g., one PRS occurrence every 160 subframes). Within a subframe containing the PRS, the PRS
are transmitted on more subcarriers and more OFDM symbols when compared to the
regular cell-specific reference signals being sent on an antenna. Utilization of more time-frequency resources
within a subframe by the PRS can improve the quality of the UE measurements
compared to the use of only the basic cell-specific reference signals. A pseudo-random sequence is sent on the PRS,
and, this sequence is a function of numerous factors such as PCI (Physical
layer Cell Identity), slot number, OFDM symbol number, and the value of Cyclic
Prefix. The UE observes the PRS from
different cells in the neighborhood and makes certain measurements. Examples of such measurements include OTDOA
(Observed Time Difference of Arrival) measurements such as RSTD (Reference
Signal Time Difference). RSTD is the
relative timing difference between a neighbor cell and the reference cell. The E-UTRAN processes these OTDOA
measurements from the UE in an implementation-specific and non-standardized
manner to estimate the UE location.
In summary, the existence of the PRS enables the UE to make
OTDOA measurements. These measurements
are then used by the E-UTRAN to determine the UE location as part of a
UE-assisted positioning technique.
References: TS36.211, TS 36.133, TS36.214, TS36.331,
Hi, really helpful article.... i had some follow-up questions...
In the specs it says that the frequency coordinate "k" is
determined by something like
6*(m + Ndl_RB - Nprs_RB)...
i am not very clear about Nprs_RB, what it actually means, isnt
Nprs_RB and Ndl_RB are same in this case?
Also how is this equation taking care of the fact that it shouldnt
write over the RE's reserved for PBCH and PSS and SSS?