Is LTE-U DOA?

LTE-U vs Wi-FiReading some of the literature about LTE-U (and LAA) leads you to believe that its deployment is a foregone conclusion: operators love it; vendors support it, and products will be available within months. But operators lack the sales channel into the enterprise where LTE-U is envisioned to be deployed and provide most value.

While LTE-U may find its way into the handset fairly rapidly, its path into the Wi-Fi access nodes will be long and arduous as that ecosystem is not particularly friendly to LTE-U (Cisco for example), while the channels of the small cell vendors, such as Huawei and Ericsson, into the enterprise are less established.  Read more of this post

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LTE Flavors in Unlicensed Spectrum

LTE-U LAA

Guest post by Faris Alfarhan*

The unprecedented increase in demand for high-speed broadband requires a bundle of solutions to satisfy the demanded capacity. Unlicensed spectrum is increasingly considered by cellular operators, internet service providers, and businesses as part of solution set. Unlicensed spectrum cannot match the quality of licensed spectrum, as the interference profile is much more stochastic. However, unlicensed spectrum offers a complimentary solution to licensed carriers for operators, and an opportunity to cable companies and internet service providers – who typically don’t own any licensed spectrum – to deploy wireless networks and hotspots. Read more of this post

Can Device-to-Device Communications Extend into the Home and SME?

DSL LTE BondingDSL and LTE bonding is a technology that have been hovering under the radar, not receiving the attention it deserves. A few operators have been experimenting with it, and some deployed it. Vodafone targets the solution at the enterprise sector, while Deutsch Telekom sees it as complementary service in rural areas. DSL/LTE bonding combines a DSL modem with a LTE UE modem at the user side along with integration in the core network to allow supplementing the service of one technology where the other falls short. It reduces bottlenecks in performance so for example when xDSL service slows to a crawl it taps the capacity of LTE. Having two separate links to the Internet creates redundancy of service and consequently increases reliability and quality of service. DSL/LTE bonding is a great technology, but I wonder if it can extend further to provide for additional applications. Specifically, can it be used as a platform for future device-to-device (D2D) communication? Read more of this post

Further Enhanced ICIC (FeICIC)

FeICIC LTE-AdvancedGuest post by Faris Alfarhan*

In an earlier post, R10-LTE enhanced inter-cell interference coordination (eICIC) techniques for heterogeneous networks were discussed, along with the concept of small cell range expansion. The purpose of cell range expansion is to offload more traffic from macro cells to small cells and hence achieve larger cell splitting gains. By adding a cell selection bias, the service area of small cells increases and more users are offloaded to small cells. The need for heterogeneous networks interference management schemes stems from the fact that users in the small cell range expansion area are vulnerable to stronger interference signals than useful signals from the associated serving small cell. In the previous post, it was explained how time domain partitioning based eICIC schemes – known as Almost Blank Subframes (ABS) – could be used to control the interference on the data channels in the range expansion region. Further, carrier aggregation based techniques – known as Cross Carrier Scheduling – could be used to control interference on the control channels (such as the PDCCH, PCFICH, and PHICH channels). However, R10 eICIC schemes did not address interference control on cell-specific reference signals (CRS), which cannot be blanked in order to ensure backward compatibility with R8 and R9 UEs. In this post, R11 improvements to eICIC schemes are discussed, along with the shortcomings of R10 eICIC schemes. First, the concept of Reduced Power Almost Blank Subframes (RP-ABS) is explained along with its advantages over ABS. I then discuss the R11 techniques of Further enhanced ICIC (FeICIC) to control the interference on CRS resources. Read more of this post

Carrier Aggregation and the Road to Cognitive Radio and Superwide Spectrum

Carrier AggregationOften, the least hyped technologies are the most effective, get the widest adoption, and have the greatest impact. Carrier aggregation is one such technology that I don’t think it received its fair share of attention. LTE did bring a number of new features that were not available in 3G, such as MIMO. But MIMO was already deployed in other technologies including both Wi-Fi and WiMAX. Carrier aggregation on the other hand developed by the requirement to achieve higher data rates in LTE network. True channel bonding is a feature of Wi-Fi, but it applies to adjacent channels. Carrier aggregation on the other hand combines distinct channels in different bands. From that perspective, I am not aware of any wireless technology that has implemented carrier aggregation. Read more of this post

An Evaluation of LTE Frequency Selective Scheduling

Guest post by Faris Alfarhan*

Frequency selective scheduling

Channel dependent scheduling is commonly used in cellular systems. In LTE, orthogonal frequency division multiple access (OFDMA) in the downlink and single carrier frequency division multiple access (SC-FDMA) in the uplink allow scheduling to be performed orthogonally in both the frequency and time domains. Instead of exploiting the frequency diversity of the channel, frequency-selective scheduling leverages the channel’s time and frequency selectivity to allocate valuable radio resources in an optimal manner. The OFDMA and SC-FDMA shared channel transmissions incorporated in LTE offer great flexibility for integrating adaptive scheduling strategies. The minimum resource allocation corresponds to a resource block of 180 kHz and a time duration of 0.5 ms. Downlink resource allocation relies on the channel quality index (CQI) reported by the user. For frequency selective scheduling to be applicable, the CQI must be reported for all of the carrier’s resource blocks. Read more of this post

On LTE-Advanced and Carrier Aggregation

LTE-AdvancedNews of LTE-Advanced is making headlines. SK Telecom aggregated two 10 MHz carriers in 800 and 1800 MHz to achieve 150 Mbps downlink throughput with a version of the Samsung Galaxy S4 handset built upon Qualcomm’s Snapdragon 800 SoC. Verizon announced that its LTE network is nearly complete and suggested carrier aggregation (CA) is the next step. AT&T on the other hand has plans to use carrier aggregation over its 700 MHz unpaired lower D and E blocks. Read more of this post