Curr - Prev - Next Record Operation

DECLARE @T_SiteRoute TABLE (RouteOrder INT,RouteOrderRank int,DeviceGroupName NVARCHAR(50))

INSERT INTO @T_SiteRoute(RouteOrder, DeviceGroupName)
SELECT RouteOrder = 1, DeviceGroupName = '4G'
UNION All SELECT RouteOrder = 2, DeviceGroupName = '3G'
UNION All SELECT RouteOrder = 3, DeviceGroupName = 'CSR'
UNION All SELECT RouteOrder = 4, DeviceGroupName = 'LR1'
UNION All SELECT RouteOrder = 5, DeviceGroupName = 'LR2'
UNION All SELECT RouteOrder = 6, DeviceGroupName = 'LR3'
UNION All SELECT RouteOrder = 7, DeviceGroupName = 'LR4'
UNION All SELECT RouteOrder = 8, DeviceGroupName = 'MR1'
UNION All SELECT RouteOrder = 9, DeviceGroupName = 'MR2'
UNION All SELECT RouteOrder = 10, DeviceGroupName = 'MR3'
UNION All SELECT RouteOrder = 11, DeviceGroupName = 'HR1'
UNION All SELECT RouteOrder = 12, DeviceGroupName = 'HR2'
UNION All SELECT RouteOrder = 13, DeviceGroupName = 'EXFO'

UPDATE T1 SET T1.RouteOrderRank = T2.RouteOrderRank
FROM @T_SiteRoute T1
INNER JOIN (
SELECT T.RouteOrder ,
       RouteOrderRank = ROW_NUMBER() OVER (ORDER BY T.RouteOrder) ,
       T.DeviceGroupName
FROM @T_SiteRoute T
) T2 ON T1.RouteOrder = T2.RouteOrder

SELECT
    Curr.RouteOrderRank
    ,Curr_DeviceGroupName = Curr.DeviceGroupName
,Nxt_DeviceGroupName = nxt.DeviceGroupName
FROM @T_SiteRoute Curr
LEFT OUTER JOIN @T_SiteRoute Nxt ON
Nxt.RouteOrderRank = (SELECT MIN(RouteOrderRank) FROM @T_SiteRoute WHERE RouteOrderRank > Curr.RouteOrderRank)

SELECT
    Curr.RouteOrderRank
    ,Curr_DeviceGroupName = Curr.DeviceGroupName
,Prev_DeviceGroupName = Prev.DeviceGroupName
FROM @T_SiteRoute Curr
left OUTER JOIN @T_SiteRoute Prev ON
curr.RouteOrderRank = (SELECT MIN(RouteOrderRank) FROM @T_SiteRoute WHERE RouteOrderRank > Prev.RouteOrderRank)