As LTE evolves, many new bands has been added. In Release 13, several new bands including the Band 66 were added as shown below. Band 66 is the one this page is about. Its difficulty turns out to be a numbering problem rather than a radio one.

The band itself is ordinary. What made it worth a note is its number, because both the band number and the channel numbers land outside the fields LTE originally reserved for them. This page follows that problem from the frequency table through to the RRC messages that had to change.

• Where is Band 66, and how wide is it ?
• Why does Band 66 need a note of its own ?
• Overlapping with existing bands
• RRC Message Issues
• Reference

Where is Band 66, and how wide is it ?

Two rows of two specification tables carry everything the radio needs to know. The first fixes where the band sits and how it is duplexed. The second fixes which channel bandwidths are allowed in it. Read them together before the rest of this page, because the awkward part of Band 66 is not in either of them.

< [36.521-1 V13.2.0] - Table 5.2-1: E-UTRA operating bands >

Read the Band 66 row across and compare its two halves. The uplink runs from 1710 MHz to 1780 MHz, which is 70 MHz wide. The downlink runs from 2110 MHz to 2200 MHz, which is 90 MHz. The band is deliberately asymmetric, with 20 MHz more downlink than uplink, and the duplex mode is FDD.

The Band 65 row directly above is worth a glance for contrast. It has the same 2110 MHz to 2200 MHz downlink but a completely different uplink, at 1920 MHz to 2010 MHz. Two bands can therefore share a downlink range and share nothing in the uplink.

< [36.521-1 V13.2.0] - Table 5.4.2.1-1: E-UTRA channel bandwidth >

The bandwidth row says something the frequency row does not. Band 66 carries a Yes in every column. All six E-UTRA channel bandwidths are allowed in it: 1.4, 3, 5, 10, 15 and 20 MHz. Band 65 on the row above allows only 5 MHz and wider. A narrow 1.4 MHz or 3 MHz carrier is therefore legal on Band 66 and not on its neighbour.

• The band is asymmetric by design : 70 MHz of uplink against 90 MHz of downlink, which is 20 MHz more downlink than uplink.
• Band 66 allows every channel bandwidth : 1.4, 3, 5, 10, 15 and 20 MHz are all marked Yes, while Band 65 starts at 5 MHz.
• A shared downlink does not mean a shared uplink : Band 65 has the same 2110 to 2200 MHz downlink and an uplink nowhere near Band 66's.

Why does Band 66 need a note of its own ?

The two tables above look unremarkable. Band 66 adds spectrum, it is duplexed the ordinary way, and it allows every channel bandwidth LTE defines. A transceiver covering those two frequency ranges needs no new technique to work in the band.

So what ?

Is there anything special with Band 66 that gets you to create a special note like this ?

In terms of Hardware implementation, I don't think there is any special about this band. It is just addition of a new frequency spectrum.

However, there is a special things about Band 66 in terms of the number. EARFCN (Channel Number) for Band 66 is from 66436 through 67335. In the original ASN design for LTE, they allocated 6 bits (1~64) for Band Indicator and 16 bits (0~65535) for EARFCN. It means, in order to specify Band 66 we need a little bit of redesign RRC message specification (ASN specification) about Band Indicator and EARFCN settings. In this page, I will summarize several issues of Band 66 (mainly with the perspective of RRC message)

It is worth putting exact limits under that paragraph, because both of them come from 36.331 and both are easy to check.

The band number travels in FreqBandIndicator, and 36.331 defines it as INTEGER (1..maxFBI) with maxFBI set to 64. Sixty-four values need six bits, and the largest band the field can name is 64. Band 66 is past the end of it.

The carrier frequency travels in ARFCN-ValueEUTRA, defined as INTEGER (0..maxEARFCN) with maxEARFCN set to 65535. That is the sixteen bits the paragraph above mentions, and the largest EARFCN the field can name is 65535. 36.101 Table 5.7.3-1 gives Band 66 a downlink EARFCN range of 66436 to 67335 and an uplink range of 131972 to 132671. Every one of those numbers is past the end of the field as well.

One detail in 36.101 fits neatly beside this. Band 64 is listed as Reserved, and no frequencies are given for it. That sits well with the signalling, because 36.331 gives the value 64 the job of announcing an extension. A band actually numbered 64 could not be indicated by the base IE at all.

• The radio is ordinary and the numbering is not : Band 66 needs no new transceiver technique. Both of its identifiers overflow the fields meant to carry them.
• FreqBandIndicator stops at 64 : 36.331 defines it as INTEGER (1..maxFBI) with maxFBI set to 64, which is six bits.
• ARFCN-ValueEUTRA stops at 65535 : that is the sixteen-bit limit, and Band 66 starts at EARFCN 66436 in the downlink.
• Band 64 is Reserved : the value 64 is spent on announcing the extension, so it was never available as a band number.

Overlapping with existing bands

First, let's get a brief overview of frequency range of Band 66 and check if it is overlapping with any existing bands. As indicated in the table below, Band 66 overlaps completely or partially with several other bands. In some case, it overlapps only downlink part (red) and in some other case it overlaps only uplink part. Of course, there are some cases where it overlaps both uplink and downlink spectrum.

The drawing repays being read as three groups rather than seven rows. Red marks a downlink range that falls inside Band 66's downlink, and blue marks an uplink range that falls inside Band 66's uplink.

Bands 1 and 65 are coloured on the downlink alone. Both sit inside 2110 to 2200 MHz, and both have uplinks far away from 1710 to 1780 MHz. Bands 3 and 9 are the mirror case, coloured on the uplink alone, with downlinks near 1800 MHz that Band 66 never reaches.

Bands 4 and 10 are coloured on both halves, and they are the interesting pair. Band 4 runs 1710 to 1755 MHz up and 2110 to 2155 MHz down. Band 10 runs 1710 to 1770 MHz up and 2110 to 2170 MHz down. Both fit entirely inside Band 66 at both ends, so Band 66 is a superset of each of them rather than merely a neighbour. The table below sets the same information out row by row.

The practical consequence belongs with the RRC discussion further down. One physical carrier can be described by more than one band number. The band a cell advertises is therefore a signalling choice as much as a hardware fact.

• Two bands sit wholly inside Band 66 : Band 4 and Band 10 overlap on both the uplink and the downlink, so Band 66 contains them.
• Two overlap on the downlink only : Band 1 and Band 65 share downlink spectrum while their uplinks are nowhere near Band 66's.
• Two overlap on the uplink only : Band 3 and Band 9 share uplink spectrum and place their downlinks around 1800 MHz.
• One carrier can carry more than one band number : the overlap makes the advertised band a signalling decision, not only a property of the radio.

RRC Message Issues

As I mentioned at the beginning, 3GPP ASN was not designed to specify this kind of big number like Band 66, EARFCN 66866 etc. So they need to revise ASN structure of some RRC messages to specify these big numbers. In this section, I will list the RRC messages that uses this newly added IE (Information Element).

• LTE - SIB 1
• LTE - SIB 5
• LTE - RRC Connection Reconfiguration (Adding B66 SCC)
• WCDMA - SIB 19

LTE - SIB 1

As you may know, you need to configure the band indicator in SIB1. To specify the Band greater than 64, a new IE in red is added. To make the red part take effect, you have to set the max value in the existing IE marked in blue.

< SIB1 > RRC capture. Field values come from a live capture, not from the specification.

systemInformationBlockType1
     cellAccessRelatedInfo
         plmn-IdentityList: 1 item
             Item 0
                 PLMN-IdentityInfo
         trackingAreaCode: 0001
         cellIdentity: 00000010
         cellBarred: notBarred (1)
         intraFreqReselection: allowed (0)
         .... ..0. csg-Indication: False
     cellSelectionInfo
         q-RxLevMin: -110dBm (-55)
     p-Max: 23dBm
     freqBandIndicator: 64
     schedulingInfoList: 3 items
     si-WindowLength: ms20 (5)
     systemInfoValueTag: 0
     nonCriticalExtension
         lateNonCriticalExtension: 6008
             SystemInformationBlockType1-v8h0-IEs
                 nonCriticalExtension
                     freqBandIndicator-v9e0: 66
         nonCriticalExtension

LTE - SIB 5

SIB5 specifies interfrequency neighbour cell info . To specify the EARFCN greater than 65535, a new IE in red is added. To make the red part take effect, you have to set the max value in the existing IE marked in blue.

< SIB5 > RRC capture. Field values come from a live capture, not from the specification.

sib5
    interFreqCarrierFreqList: 1 item
        Item 0
            InterFreqCarrierFreqInfo
                dl-CarrierFreq: 65535
                q-RxLevMin: -110dBm (-55)
                p-Max: 23dBm
                t-ReselectionEUTRA: 0s
                threshX-High: 4dB (2)
                threshX-Low: 2dB (1)
                allowedMeasBandwidth: mbw25 (2)
                .... .0.. presenceAntennaPort1: False
                cellReselectionPriority: 4
                neighCellConfig: No MBSFN subframes are present in all neighbour cells (1)
                q-OffsetFreq: dB3 (18)
    lateNonCriticalExtension: 6100a8c0
        SystemInformationBlockType5-v8h0-IEs
            nonCriticalExtension
                interFreqCarrierFreqList-v9e0: 1 item
                    Item 0
                        InterFreqCarrierFreqInfo-v9e0
                            dl-CarrierFreq-v9e0: 66886

LTE - RRC Connection Reconfiguration (Adding B66 SCC)

When you set up Carrier Aggregation with B66 as a SCC, you need to specify B66 EARFCN (big number greater than 65535). To specify the EARFCN greater than 65535, a new IE in red is added. To make the red part take effect, you have to set the max value in the existing IE marked in blue.

< RRC Connection Reconfiguration > RRC capture. Field values come from a live capture, not from the specification.

rrcConnectionReconfiguration
    rrc-TransactionIdentifier: 0
    criticalExtensions: c1 (0)
        c1: rrcConnectionReconfiguration-r8 (0)
            rrcConnectionReconfiguration-r8
                radioResourceConfigDedicated
                    mac-MainConfig: explicitValue (0)
                        ....
                    physicalConfigDedicated
                        pusch-ConfigDedicated
                            ...
                        pucch-ConfigDedicated-v1020
                            pucch-Format-r10: channelSelection-r10 (1)
                                channelSelection-r10
                                    n1PUCCH-AN-CS-r10: setup (1)
                                        setup
                                            n1PUCCH-AN-CS-List-r10: 2 items
                                                ...
                nonCriticalExtension
                    nonCriticalExtension
                        nonCriticalExtension
                            sCellToAddModList-r10: 1 item
                                Item 0
                                    SCellToAddMod-r10
                                        sCellIndex-r10: 1
                                        cellIdentification-r10
                                            physCellId-r10: 0
                                            dl-CarrierFreq-r10: 65535
                                        radioResourceConfigCommonSCell-r10
                                            ...
                                        radioResourceConfigDedicatedSCell-r10
                                            physicalConfigDedicatedSCell-r10
                                                nonUL-Configuration-r10
                                                    ...
                                                ul-Configuration-r10
                                                    cqi-ReportConfigSCell-r10
                                                        ...
                                        dl-CarrierFreq-v1090: 66886

WCDMA - SIB 19

The Band 66 forced the ASN changes not only for LTE but also for WCDMA. WCDMA SIB 19 carries the neighbour cell of different radio technolgies. To configure Band 66 frequencies in SIB 19, SIB 19 should be revised as follows. To specify the EARFCN greater than 65535, a new IE in red is added. To make the red part take effect, you have to set the max value in the existing IE marked in blue

< WCDMA SIB 19 > RRC capture. Field values come from a live capture, not from the specification.

SysInfoType19
    utra-PriorityInfoList
        utra-ServingCell
            priority: 0
            s-PrioritySearch1: 0
            threshServingLow: 0
    eutra-FrequencyAndPriorityInfoList: 1 item
        Item 0
            EUTRA-FrequencyAndPriorityInfo
                earfcn: 65535
                priority: 0
                qRxLevMinEUTRA: -64
                threshXhigh: 0
                threshXlow: 0
                ...0 .... eutraDetection: False
    v920NonCriticalExtensions
        sysInfoType19-v920ext
            utra-PriorityInfoList-v920ext
            eutra-FrequencyAndPriorityInfoList-v920ext: 1 item
                Item 0
                    EUTRA-FrequencyAndPriorityInfo-v920ext
        va80NonCriticalExtensions
            sysInfoType19-va80ext
            vb30NonCriticalExtensions
                sysInfoType19-vb30ext
                vb50NonCriticalExtensions
                    sysInfoType19-vb50ext
                        eutra-FrequencyAndPriorityInfoExtensionList: 1 item
                            Item 0
                                EUTRA-FrequencyAndPriorityInfoExtension-vb50ext
                                    earfcn: 66866
                                    measurementBandwidth: mbw75 (4)
                                    priority: 7
                                    qRxLevMinEUTRA: -62
                                    threshXhigh: 4
                                    threshXlow: 2
                                    0... .... eutraDetection: False

One rule sits behind all four captures, and 36.331 states it in a single line for each field. For the field without a suffix, the value maxFBI indicates that the frequency band is indicated by means of an extension. The value maxEARFCN says the same thing about the E-UTRA carrier frequency.

That is what the blue values in the captures are doing. A blue 64 or a blue 65535 is not a band or a frequency at all. It is a sentinel, and it tells the reader to look in the extension for the real number. Leave the blue field at anything else and the red field is ignored, however correct the number in it looks. The four ranges line up like this.

Two things follow from the ranges. The extension does not simply widen the old field, because it starts where the old one stops and the two never overlap. A UE that does not implement the extension cannot be configured for these bands at all. The only value the base field can offer such a UE is the sentinel.

• The blue value is a sentinel, not a number : 36.331 gives maxFBI and maxEARFCN one job, which is to announce that the real value sits in an extension.
• Set the sentinel or the extension is ignored : leave the base field at any other value and the UE reads that value, skipping the red field.
• The ranges abut rather than overlap : the extensions run from 65 and from 65536, so no number can be expressed in both fields.
• Band 66 is not only an LTE change : the WCDMA capture above shows the same pattern, because a UTRAN cell points at these carriers too.

Reference

Two specifications carry the numbers quoted on this page. The clause and table numbers sit beside each claim, so the wording can be checked rather than taken on trust.

• 36.331 - Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC) protocol specification. FreqBandIndicator, FreqBandIndicator-v9e0, ARFCN-ValueEUTRA and ARFCN-ValueEUTRA-v9e0 are defined there, together with the constants maxFBI, maxFBI2, maxEARFCN and maxEARFCN2. The rule that the maximum value announces an extension is stated there too.
• 36.101 - Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception, v20.0.0. Table 5.7.3-1 gives Band 66 a downlink EARFCN range of 66436 to 67335 and an uplink range of 131972 to 132671. The same table lists band 64 as Reserved.