Carrier aggregation -

Carrier aggregation – (one) key enabler for LTE-Advanced Analysts anticipate that by the end of 2012, 152 LTE networks will be on air in 68 countries worldwide. Compared to previous technology rollouts (2G, 3G, 3.5G), this is by far the fastest adaptation that the wireless industry has seen to date. But even with all marketing departments of all network operators advertising today’s LTE deployments as 4G, speaking strictly technical – they are not. LTE in its definition as of 3GPP Release 8 does not meet all IMT-Advanced requirements as set by ITU to be designated a true 4G mobile communications...

within LTE: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz or 20 MHz. This of course depends on the availability of spectrum to each individual network operator. Currently, RAN4 discusses constellations with 5 MHz, 10 MHz, 15 MHz and 20 MHz channel bandwidth. As none of these service providers owns a continuous spectrum of 100 MHz, three different modes of carrier aggregation exist within L ­ TE‑Advanced: intraband contiguous, intraband non-contiguous and interband carrier aggregation. Rel-10 already Figure 1  Modes of carrier aggregation Intraband contiguous Frequency band A Intraband non-contiguous...

Are all component carriers equal? The important question is how carrier aggregation is activated by the network. The answer is simple: only in connected mode. So before this can actually take place, a mobile device that supports Rel‑10 needs to execute the generic access procedures that are defined for LTE as of Rel-8: cell search and selection, system information acquisition and initial random access. All these procedures are carried out on the Primary Component Carrier (PCC) for downlink and uplink. Secondary Component Carriers (SCC) – in total up to four, initially two – are seen as additional...

What type(s) of carrier aggregation does a device support? At this point it is important to note that there are certain limitations as to what band combinations a Rel-10-capable terminal can support. A multitechnology device enabled for global roaming has to support at least four GSM frequency bands, five 3G/WCDMA frequency bands and three LTE bands, if we just consider 3GPP-defined technology support. Not to mention the support of GPS, FM, Bluetooth® and WLAN standards, and eventually NFC 4). Each technology requires its own transmit-receive (TRX) chain, and space is limited due to the form...

Impact of carrier aggregation on LTE signaling procedures Generally speaking, the signaling for carrier aggregation affects only certain layers, not the entire protocol stack. For instance, the device is permanently connected via its PCC to the serving Primary Cell (PCell). Non-Access S ­ tratum (NAS) functionality such as security key exchange and mobility information are provided by the PCell. All secondary component carriers, or secondary cells, are understood as additional transmission resources. For the Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) layer, carrier aggregation...

as well as common and dedicated information. For the common and dedicated information, the transferred information is separated for downlink and uplink. Common information means it is applicable to all devices that this carrier will be added to, including for instance its bandwidth, PHICH and PDSCH configuration and, in the case of TD-LTE, the UL-DL configuration and special subframe configuration. Further, the MBSFN subframe configuration is part of the downlink information. With Rel-9, broadcast/ multicast capabilities have been fully defined for LTE and summarized as enhanced Multimedia Broadcast...

This information, referred to as PDSCH-Start 7), needs to be signaled to the device during activation of cross-carrier scheduling and is therefore part of the related information element. Depending on the bandwidth of the component carrier, this could be anywhere from 1 to 4 OFDM symbols. For cross-carrier scheduling, it is also important to point out that if resources on a component carrier are scheduled via another carrier, e.g. the PCC, no resources on that SCC for that terminal can be scheduled by any o ­ ther component carrier. However, initial deployments with carrier aggregation will utilize...

used today in many development labs around the world to perform full protocol conformance testing according to the relevant 3GPP specification81. A certain number of test cases require the simulation of multiple cells of different ity testing, PLMN and cell selection scenarios or neighbor cell measurements. Investing in a multibox setup will pay off as it will be reused for mobility testing for carrier aggre- gation, including 2x2 MIMO or even 4x2 MIMO, which is already supported today as defined in LTE as of Rel-8. Another option for testing the LTE physical layer with a focus on carrier aggregation...

Figure 9  Setup measuring TAE for interband carrier aggregation with Rohde & Schwarz signal and ­spectrum analyzer Outlook: carrier aggregation enhancements with 3GPP Releases 11 and 12 While Rel-10 carrier aggregation is currently in the implementation phase, the 3GPP standardization is working on new CA features and enhancements for the next release (Rel-11). The core work item “LTE Carrier Aggregation E ­ nhancements” in all its details will not be finalized before December 2012. Nevertheless, RAN1 has already decided on the basic functionality, features and changes. We present a brief preview...

Andreas Roessler is Technology Manager Meik Kottkamp is Technology Manager within the Test & Measurement Division within the Test & Measurement Division of Rohde & Schwarz in Munich, Germany. He ­ M ­ unich, Germany. He is dedicated to the is responsible for strategic marketing and North American market (US & Canada) with product portfolio development for LTE, a ­ ocus on UMTS Long Term Evolution f L ­ TE‑Advanced, HSPA+ and EDGE Evolu- tion. He joined Rohde & Schwarz in August ­ for strategic marketing and product port- folio development for LTE/LTE-Advanced. Siemens Mobile Communication Net-...