Use Cases for the 2.5/2.6 GHz Spectrum: Options for TDD Band 38

Large amounts of spectrum in the 2.5-2.7 GHz band are available now for mobile network deployments. Spectrum auctions in Europe in the past two years made much of the 190 MHz available to network operators. This band sold at a significant discount to the 800 MHz band (between 5 – 35x). While in the United States Clearwire used this band to deploy WiMAX, in Europe, operators are unanimous of LTE. So, what are the deployment options?

The 2.5/2.6 GHz FDD band can be used either as a macro-layer network or as an underlay small cell network complementing macrocells that operate at lower frequencies. The TDD band (referred to as TDD Band 38 which spans 2.57-2.62 GHz) can be used in either such mode using TD-LTE; additionally, it provides two new options: carrier aggregation to complement a 2.5/2.6 GHz network or wireless backhaul of small cells. I will address the macro vs. micro cell option in a future post and focus here on the carrier aggregation and small cell backhaul options.

FDD Band

(2500-2570 / 2620-2690 MHz)

TDD Band

(2570 – 2620 MHz)

Macrocells

Y

Y

Micro/Picocells (HetNets)

Y

Y

Carrier Aggregation

N/A

Y

Wireless Backhaul

X

Y

Carrier aggregation would be an option if the same operator owns both TDD and FDD spectrum. I don’t think the ecosystem is ready yet for carrier aggregation in different bands as it entails an additional RF front end adding to a long list of frequencies in LTE that can only contribute to slow down adoption. The heavy requirements on download capacity projected by virtue of video being the dominant traffic application adds to the value proposition of this approach.

Small cell wireless backhaul is another alternative especially if the TDD spectrum is owned by the same operator that owns 2.5 GHz FDD spectrum. This fits well the model of using the FDD band for small cell deployments. To enable this application, the operator would need a reasonable amount of spectrum; hence, an operator holding a very small chunk like 5 MHz which is insufficient for wireless backhaul would opt for carrier aggregation.

The use options for 2.5 GHz band vary significantly depending on who and how much spectrum is owned and can only be determined in the context of a greater business plan and strategy. This is very different from lower “beachfront” spectrum in the 700 and 800 MHz bands where LTE macro-cellular architecture is the uncontested deployment mode.

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About Frank Rayal
Telecom industry management consultant.

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