Ray joined Award Solutions in 2006, bringing his expertise in CDMA technologies and overall experience in real-time product development, delivery and support of wireless telecommunications systems. He has over 20 years of experience in the wireless telecom industry. At Award Solutions, he specializes in 4th generation telecommunications systems, with a focus on WiMAX technology, engineering and deployment.
Ray began his career working on real-time embedded software development in data communications for computer numerical controls. He then joined Nortel and worked on IBM-compatible data terminal systems development and other proprietary data communications systems for 8 years. He then moved into development for class 5 switching systems and followed that with more than 16 years in various development and support roles in wireless telecommunication systems.
As a senior designer at Nortel, Ray worked on the development of real-time call processing and OA&M software development for AMPS and TDMA. As a manager and senior manager for CDMA development, he managed teams that developed and delivered the first deployment of the CDMA IS-95B BSC product and also delivered products based on the CDMA2000 1XRTT standard. He has also worked on stress test tool development for testing and analysis of link capacity in wireless networks. He has also worked on OA&M development and deployment tools for Nortel’s Media Gateway product. Ray has received numerous awards within Nortel for his work on CDMA new product development and performance improvements.
Ray’s position at Award Solutions puts him at the forefront of emerging technologies with an emphasis on WiMAX technology and deployment. He has extensive knowledge of Mobile WiMAX standards and hands-on experience with engineering and deployment teams. As part of Ray’s expertise in WiMAX technology, he was awarded a Qualified Specialist certification from Cisco as an approved installation, commissioning and field engineer for their BWX WiMAX product. He is also an approved instructor for Cisco’s BWX Broadband Wireless Access System.
Ray received his Bachelor’s degree in Computer Science (with Distinction) from Wayne State University in Detroit, Michigan.
This is part 2 of my blog series about PDSCH transmission modes for the UE’s C-RNTI.
Transmission mode 1 (tm1) is one of the default transmission modes if a transmission mode is not specifically configured for a UE. In that case, if only one antenna port is used for PBCH transmission in the cell, then the UE defaults to tm1. Based on this particular case, you could assume that this cell only has one transmit antenna (not a normal LTE deployment for cellular services).
Transmission Mode 1 (from 3GPP TS 36.213)
“Single-antenna port, port 0” means that all DL transmissions to this UE are sent using only antenna port 0 even if the cell has more than one transmit antenna. This transmission scheme limits the DL performance for this UE. Without multiple antenna techniques, such as “transmit diversity” or MIMO, this device does not get the benefit of a robust signal at the cell edge or increased throughput using MIMO.
Just because the cell would only use one transmit antenna, it doesn’t limit the UE to only one receive antenna. The UE could be using either one (SISO1 transmission from the cell) or two (SIMO2 transmission from the cell) receive antennas. With SIMO, a UE could use receive diversity techniques to improve DL coverage but a UE that has only one receive antenna (possibly an inexpensive category 1 UE for monitoring applications) would be limited to SISO transmission in the DL.
Let’s look at this in another way. Let’s assume we have a cell where it only has one transmit antenna. Then tm1 is required for all devices in that cell. This would impact the DL performance and cell coverage for all of the devices. Without support for transmit diversity, this would probably shrink the size of the cell coverage area. This would be a very limited usage cell (not used for high speed multi-media services) with few users. It would probably be in a private network for spot coverage for occasional use by a few users that do not require high-speed services in either direction (uplink or downlink). Or maybe this could be a cell with lower equipment costs that mainly performs remote equipment monitoring possibly for machine-to-machine (M2M) applications and provides basic communications for any support workers.
Another scenario for tm1 could be an existing cell used for “normal” broadband cellular services with multiple antennas is also used to monitor machines (specifically configured with tm1) where uplink transmission is only a couple of short bursts per day and even less frequent DL transmission (maintenance commands).
Maybe tm1 could also be used in an inexpensive femtocell with limited number of users. Anybody else have any other possible scenarios?
With tm1, the UE searches the common search space of PDCCH to find DCI format 1A records destined for its C-RNTI and the UE-specific search space for both DCI format 1 and 1A records identified by its C-RNTI. These searches are combined with any other searches the UE needs to do for other RNTI values (e.g., SPS C-RNTI, TPC-PUCCH-RNTI, etc.) and also any searches for DCI format 0 records.
Tm1 also impacts UE feedback. Obviously, since the UE is only receiving data from one antenna at the cell, there is no need for PMI or RI feedback. Transmission mode 1 limits a UE to report the associated CQI value based on only the one antenna port. This is a good thing if you want a low-cost device!
So in the case of tm1, 1 means one antenna and isn’t really the #1 transmission mode! BUT…..it does have potential uses for low-speed monitoring applications or low-cost femtocells. In those cases one antenna is more than enough. Maybe tm1 is the tm version of the “little engine that could”!
I’ll continue this blog series in the near future with a discussion of transmission mode 2.
Ray
1 SISO = Single Input Single Output (transmitter using one antenna and receiver using one antenna)
2 SIMO = Single Input Multiple Output (transmitter using one antenna and receiver using multiple antennas)