NTT Docomo gives another shot to Mobile TV

Couple of news items from earlier this month from Japan about the nottv Mobile TV service. First was that it celebrated its 1st anniversary. The second is that it has racked up 700,000 subscribers; less than a million that it was expecting. I have posted in the past about attempts by various parties on Mobile TV that was unsuccessful. You can read more about that here and here.

One of the ways Mobile TV can provide additional value as compared to the normal TV is through audience participation. NOTTV is working to be able to provide this feature in future. Also it uses the ISDB-Tmm standard for broadcast. Hopefully in future when eMBMS is more popular, it may be used to transmit Mobile TV data as well. A picture showing the difference between the ISDB-T and ISDB-Tmm is shown below (from the presentation here)

A magazine article on NOTTV from the NTT Docomo magazine is embedded as follows:

Service Overview of NOTTV Mobile Multimedia Broadcasting for Smartphones from Zahid Ghadialy

eMBMS Release-11 enhancements

Continuing on the eMBMS theme. In the presentation in the last post, there was introduction to the eMBMS protocols and codecs and mention about the DASH protocol. This article from the IEEE Communications magazine provides insight into the working of eMBMS and what potential it holds.

Evolved Multimedia Broadcast/Multicast Service (eMBMS) in LTE-Advanced: Overview and Rel-11 Enhancements from Zahid Ghadialy

eMBMS rollouts gathering steam in 2013

Its been a while since I last posted something on eMBMS. Its been even longer that we saw anything official from 3GPP on eMBMS. Recently I have seen some operators again starting to wonder if eMBMS makes business sense, while the vendors and standards are still working hard on the technology.

Not so long back, HEVC/H.265 codec was standardised. This codec helps transmission of the video using half the bandwidth. This means that it would be economical to use this for broadcast technologies. No wonder Nokia, Thompson and NTT Docomo are excited.

Interesting picture from a Qualcomm presentation (embedded in the end) shows how different protocols fit in the eMBMS architecture. My guess would be that the HEVC  may be part of the Codecs.

On the operators front, Korea Telecom (KT) has intentions for countrywide rollout. Korea is one of the very few countries where end users have embraced watching video on small form factors. Verizon wireless has already signalled the intention to rollout eMBMS in 2014; its working out a business case. Telenor Sweden is another player to join the band with the intention of adopting Ericsson's Multi screen technology.

One of the main reasons for the lack of support for the 3G MBMS technology was not a compelling business case. Qualcomm has a whitepaper that outlines some of the potential of LTE Broadcast technology here. A picture from this whitepaper on the business case below:

Finally, a presentation from Qualcomm research on eMBMS embedded below:

LTE eMBMS Technology Overview from Zahid Ghadialy

Cell Range Expansion (CRE)

The intention of the Pico Cells is to offload traffic from the Macro cells to increase the system capacity. As a result, when Macro cell becomes overloaded, it would make sense to offload the MUE’s in the vicinity of the Pico cell to it. This can/should be done even if the UE is receiving a better signal from the Macro cell. The expansion of the range of the Pico cell is termed as CRE or Cell Range expansion.

To make sure that the UE does not fail in the handover process, the Time domain ICIC should be used and Macro cell should use ABS. The UE’s can be configured to do measurements on the Pico when the Macro is using ABS. The MUE now reports the Measurement reports to the Macro and are handed over to the Pico to act as PUE.

Myths and Challenges in Future Wireless Access

Interesting article from the recent IEEE Comsoc magazine. Table 1 on page 5 is an interesting comparison of how different players reach the magical '1000x' capacity increase. Even though Huawei shows 100x, which may be more realistic, the industry is sticking with the 1000x figure. 

Qualcomm is touting a similar 1000x figure as I showed in a post earlier here.

Interference Management in HetNets

Interference Management is a big topic in HetNet's. An earlier blog post here on similar topic was very popular. The above picture shows a Heterogeneous cellular network topology incorporating different forms of small cell deployments as an overlay on the macrocell network. Small cells would generally use secure tunnels back to the core network using existing broadband infrastructure. Whereas in the HCS (Hierarchical Cell Structures), different layers have different frequencies, thereby not causing radio frequency interference, in HetNets same frequencies can be used between different layers. The same frequencies can cause radio frequency Interference and necessitates the use of advanced Interference avoidance techniques.

CTTC has another interesting presentation on Interference Management in HetNets that I am embedding below as slides and video:

Interference Management in Co-Channel Femtocell Deployment from Zahid Ghadialy

The 'Phantom Cell' concept in LTE-B

One of the LTE-B proposals by NTT Docomo is this 'Phantom Cell' concept. A recent article from the IEEE Communications Magazine expands this further:


Phantom Cell Concept — In the current deployments, there are a number of capacity solutions for indoor environments such as WiFi, femtocells, and in-building cells using distributed antenna systems (DAS). However, there is a lack of capacity solutions for high-traffic outdoor environments that can also support good mobility and connectivity. Thus, we propose the concept of macro-assisted small cells, called the Phantom Cell, as a capacity solution that offers good mobility support while capitalizing on the existing LTE network. In the Phantom Cell concept, the C-plane/U-plane are split as shown in Fig. The C-plane of UE in small cells is provided by a macrocell in a lower frequency band, while for UE in macrocells both the C-plane and U-plane are provided by the serving macrocell in the same way as in the conventional system. On the other hand, the Uplane of UE in small cells is provided by a small cell using a higher frequency band. Hence, these macro-assisted small cells are called Phantom Cells as they are intended to transmit UE-specific signals only, and the radio resource control (RRC) connection procedures between the UE and the Phantom Cell, such as channel establishment and release, are managed by the macrocell.

The Phantom Cells are not conventional cells in the sense that they are not configured with cell specific signals and channels such as cell-ID-specific synchronization signals, cell-specific reference signals (CRS), and broadcast system information. Their visibility to the UE relies on macrocell signaling. The Phantom Cell concept comes with a range of benefits. One important benefit of macro assistance of small cells is that control signaling due to frequent handover between small cells and macrocells and among small cells can be significantly reduced, and connectivity can be maintained even when using small cells and higher frequency bands. In addition, by applying the new carrier type (NCT) that contains no or reduced legacy cell-specific signals, the Phantom Cell is able to provide further benefits such as efficient energy savings, lower interference and hence higher spectral efficiency, and reduction in cellplanning effort for dense small cell deployments.

To establish a network architecture that supports the C/U-plane split, and interworking between the macrocell and Phantom Cell is required. A straightforward solution to achieve this is to support Phantom Cells by using remote radio heads (RRHs) belonging to a single macro eNB. This approach can be referred to as intra-eNB carrier aggregation (CA) using RRHs. However, such a tight CA-based architecture has some drawbacks as it requires single-node operation with low-latency connections (e.g., optical fibers) between the macro and Phantom Cells. Therefore, more flexible network architectures should be investigated to allow for relaxed backhaul requirements between macro and Phantom Cells and to support a distributed node deployment with separated network nodes for each (i.e., inter-eNB CA).